Fix compile error on Cygwin, where int32 is typedefed to long instead of int, and the compiler can't figure out which overload of this method to use in that case.

src/google/protobuf/stubs/common.cc

@@ -145,6 +145,8 @@ DECLARE_STREAM_OPERATOR(const char*  , )
 DECLARE_STREAM_OPERATOR(char         , SimpleCtoa)
 DECLARE_STREAM_OPERATOR(int          , SimpleItoa)
 DECLARE_STREAM_OPERATOR(uint         , SimpleItoa)
+DECLARE_STREAM_OPERATOR(long         , SimpleItoa)
+DECLARE_STREAM_OPERATOR(unsigned long, SimpleItoa)
 DECLARE_STREAM_OPERATOR(double       , SimpleDtoa)
 #undef DECLARE_STREAM_OPERATOR
 

src/google/protobuf/stubs/common.h

@@ -586,6 +586,8 @@ class LIBPROTOBUF_EXPORT LogMessage {
   LogMessage& operator<<(char value);
   LogMessage& operator<<(int value);
   LogMessage& operator<<(uint value);
+  LogMessage& operator<<(long value);
+  LogMessage& operator<<(unsigned long value);
   LogMessage& operator<<(double value);
 
  private: