Restore old compression functions to preserve ABI

Fixes #183

snappy.cc

diff --git a/snappy.cc b/snappy.cc
index 08c2a98..56b8c82 100644
--- a/snappy.cc
+++ b/snappy.cc
@@ -1792,6 +1792,10 @@
   return decompressor.ReadUncompressedLength(result);
 }
 
+size_t Compress(Source* reader, Sink* writer) {
+  return Compress(reader, writer, CompressionOptions{});
+}
+
 size_t Compress(Source* reader, Sink* writer, CompressionOptions options) {
   assert(options.level == 1 || options.level == 2);
   int token = 0;
@@ -2299,6 +2303,12 @@
 }
 
 void RawCompress(const char* input, size_t input_length, char* compressed,
+                 size_t* compressed_length) {
+  RawCompress(input, input_length, compressed, compressed_length,
+              CompressionOptions{});
+}
+
+void RawCompress(const char* input, size_t input_length, char* compressed,
                  size_t* compressed_length, CompressionOptions options) {
   ByteArraySource reader(input, input_length);
   UncheckedByteArraySink writer(compressed);
@@ -2309,6 +2319,12 @@
 }
 
 void RawCompressFromIOVec(const struct iovec* iov, size_t uncompressed_length,
+                          char* compressed, size_t* compressed_length) {
+  RawCompressFromIOVec(iov, uncompressed_length, compressed, compressed_length,
+                       CompressionOptions{});
+}
+
+void RawCompressFromIOVec(const struct iovec* iov, size_t uncompressed_length,
                           char* compressed, size_t* compressed_length,
                           CompressionOptions options) {
   SnappyIOVecReader reader(iov, uncompressed_length);
@@ -2319,6 +2335,11 @@
   *compressed_length = writer.CurrentDestination() - compressed;
 }
 
+size_t Compress(const char* input, size_t input_length,
+                std::string* compressed) {
+  return Compress(input, input_length, compressed, CompressionOptions{});
+}
+
 size_t Compress(const char* input, size_t input_length, std::string* compressed,
                 CompressionOptions options) {
   // Pre-grow the buffer to the max length of the compressed output
@@ -2332,6 +2353,11 @@
 }
 
 size_t CompressFromIOVec(const struct iovec* iov, size_t iov_cnt,
+                         std::string* compressed) {
+  return CompressFromIOVec(iov, iov_cnt, compressed, CompressionOptions{});
+}
+
+size_t CompressFromIOVec(const struct iovec* iov, size_t iov_cnt,
                          std::string* compressed, CompressionOptions options) {
   // Compute the number of bytes to be compressed.
   size_t uncompressed_length = 0;

snappy.h

diff --git a/snappy.h b/snappy.h
index bde378b..2f1b802 100644
--- a/snappy.h
+++ b/snappy.h
@@ -78,8 +78,10 @@
 
   // Compress the bytes read from "*reader" and append to "*writer". Return the
   // number of bytes written.
+  // First version is to preserve ABI.
+  size_t Compress(Source* reader, Sink* writer);
   size_t Compress(Source* reader, Sink* writer,
-                  CompressionOptions options = {});
+                  CompressionOptions options);
 
   // Find the uncompressed length of the given stream, as given by the header.
   // Note that the true length could deviate from this; the stream could e.g.
@@ -98,16 +100,22 @@
   // Original contents of *compressed are lost.
   //
   // REQUIRES: "input[]" is not an alias of "*compressed".
+  // First version is to preserve ABI.
   size_t Compress(const char* input, size_t input_length,
-                  std::string* compressed, CompressionOptions options = {});
+                  std::string* compressed);
+  size_t Compress(const char* input, size_t input_length,
+                  std::string* compressed, CompressionOptions options);
 
   // Same as `Compress` above but taking an `iovec` array as input. Note that
   // this function preprocesses the inputs to compute the sum of
   // `iov[0..iov_cnt-1].iov_len` before reading. To avoid this, use
   // `RawCompressFromIOVec` below.
+  // First version is to preserve ABI.
+  size_t CompressFromIOVec(const struct iovec* iov, size_t iov_cnt,
+                           std::string* compressed);
   size_t CompressFromIOVec(const struct iovec* iov, size_t iov_cnt,
                            std::string* compressed,
-                           CompressionOptions options = {});
+                           CompressionOptions options);
 
   // Decompresses "compressed[0..compressed_length-1]" to "*uncompressed".
   // Original contents of "*uncompressed" are lost.
@@ -151,14 +159,18 @@
   //    ... Process(output, output_length) ...
   //    delete [] output;
   void RawCompress(const char* input, size_t input_length, char* compressed,
-                   size_t* compressed_length, CompressionOptions options = {});
+                   size_t* compressed_length);
+  void RawCompress(const char* input, size_t input_length, char* compressed,
+                   size_t* compressed_length, CompressionOptions options);
 
   // Same as `RawCompress` above but taking an `iovec` array as input. Note that
   // `uncompressed_length` is the total number of bytes to be read from the
   // elements of `iov` (_not_ the number of elements in `iov`).
   void RawCompressFromIOVec(const struct iovec* iov, size_t uncompressed_length,
+                            char* compressed, size_t* compressed_length);
+  void RawCompressFromIOVec(const struct iovec* iov, size_t uncompressed_length,
                             char* compressed, size_t* compressed_length,
-                            CompressionOptions options = {});
+                            CompressionOptions options);
 
   // Given data in "compressed[0..compressed_length-1]" generated by
   // calling the Snappy::Compress routine, this routine