fix compilation errors on Visual Studio

I have separated the Visual Studio build errors from cmake (https://github.com/protobuf-c/protobuf-c/pull/155).

Here is the patch that allows compilation on Windows. It fixes 3 different (but simple) errors with following reasons:
  - use _inline for non-c99 msvc compiler
  - use char* instead of void* in pointer shifting
  - on non-gnuc family compilers DEPRECATED macros was undefined

(see also https://github.com/protobuf-c/protobuf-c/issues/168)