Make some down conversions explicit in the gz routines.

gzread.c

diff --git a/gzread.c b/gzread.c
index 52a5019..b198a44 100644
--- a/gzread.c
+++ b/gzread.c
@@ -27,7 +27,7 @@
         get = len - *have;
         if (get > max)
             get = max;
-        ret = read(state->fd, buf + *have, get);
+        ret = (int)read(state->fd, buf + *have, get);
         if (ret <= 0)
             break;
         *have += (unsigned)ret;

gzwrite.c

diff --git a/gzwrite.c b/gzwrite.c
index acea74f..18c820e 100644
--- a/gzwrite.c
+++ b/gzwrite.c
@@ -77,7 +77,7 @@
             errno = 0;
             state->again = 0;
             put = strm->avail_in > max ? max : strm->avail_in;
-            writ = write(state->fd, strm->next_in, put);
+            writ = (int)write(state->fd, strm->next_in, put);
             if (writ < 0) {
                 if (errno == EAGAIN || errno == EWOULDBLOCK)
                     state->again = 1;
@@ -112,7 +112,7 @@
                 state->again = 0;
                 put = strm->next_out - state->x.next > (int)max ? max :
                       (unsigned)(strm->next_out - state->x.next);
-                writ = write(state->fd, state->x.next, put);
+                writ = (int)write(state->fd, state->x.next, put);
                 if (writ < 0) {
                     if (errno == EAGAIN || errno == EWOULDBLOCK)
                         state->again = 1;