Change size type in AnnotateBenignRaceSized to size_t from long

This makes this definition consistent with Abseil's declarations.  See:
https://github.com/abseil/abseil-cpp/blob/master/absl/base/dynamic_annotations.h#L213-L215

Having this unsigned seems to match what libsanitizers is expecting:
16e2427f50/libsanitizer/tsan/tsan_interface_ann.cpp (L367-L371)

This solves a "conflicting declaration of C function" when using glog
with abseil.

src/glog/logging.h.in

@@ -1034,7 +1034,7 @@ extern "C" void AnnotateBenignRaceSized(
   const char *file,
   int line,
   const volatile void *mem,
-  long size,
+  size_t size,
   const char *description);
 
 namespace google {