Add missing casts to enable compilation with gcc 4.7

Change on 2014/12/16 by rsilvera <rsilvera@google.com>
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=82275653

src/compiler/ruby_generator_helpers-inl.h

@@ -44,7 +44,7 @@ namespace grpc_ruby_generator {
 inline bool ServicesFilename(const google::protobuf::FileDescriptor* file,
                              string* file_name_or_error) {
   // Get output file name.
-  static const int proto_suffix_length = 6;  // length of ".proto"
+  static const unsigned proto_suffix_length = 6;  // length of ".proto"
   if (file->name().size() > proto_suffix_length &&
       file->name().find_last_of(".proto") == file->name().size() - 1) {
     *file_name_or_error = file->name().substr(

src/cpp/util/time.cc

@@ -54,8 +54,9 @@ void Timepoint2Timespec(const system_clock::time_point& from,
 
 system_clock::time_point Timespec2Timepoint(gpr_timespec t) {
   system_clock::time_point tp;
-  tp += seconds(t.tv_sec);
-  tp += nanoseconds(t.tv_nsec);
+  tp += duration_cast<system_clock::time_point::duration>(seconds(t.tv_sec));
+  tp +=
+      duration_cast<system_clock::time_point::duration>(nanoseconds(t.tv_nsec));
   return tp;
 }