Add test for extreme integer values (INT32_MAX etc.) in AllTypes.

tests/cxx_main_program/SConscript

diff --git a/tests/cxx_main_program/SConscript b/tests/cxx_main_program/SConscript
index 4bca1b1..e78c6b3 100644
--- a/tests/cxx_main_program/SConscript
+++ b/tests/cxx_main_program/SConscript
@@ -3,6 +3,10 @@
 
 Import("env")
 
+# This is needed to get INT32_MIN etc. macros defined
+env = env.Clone()
+env.Append(CPPDEFINES = ['__STDC_LIMIT_MACROS'])
+
 # Copy the files to .cxx extension in order to force C++ build.
 c = Copy("$TARGET", "$SOURCE")
 env.Command("pb_encode.cxx", "#../pb_encode.c", c)