supporting native scalars #38

probably almost works fine. need more test cases.

[ini option]
protocolbuffers.native_scalars = 0 // default: disabled

native scalars option will little bit improve decoding performance and
reduce memory size. but it might loose precision when using big numbers.
fixed typo
Merge remote-tracking branch 'origin/support-native-scalar' into travis-fix

Conflicts:
	core.c