Added Travis CI status image

Added Travis CI yaml

Allow libcrc to be used with C++ (#20)

fix gcc7 build, allow Makefile to use extern CC variable (#7)

Added compiler warning suppression for VS2017

Merge branch 'master' of https://github.com/lammertb/libcrc

Added stddef.h header file

Format checksum as char-sized int in checksum_NMEA (#8)

Removed format truncation warning because it is not universally supported by compilers

Added extra error message for format truncation

Merge pull request #2 from garverp/gcc540_fix

Fixes fgets() return value is never used. On gcc 5.4.0, causes a compile error because warnings are treated as errors in the default Makefile. Otherwise, need -Wno-unused-result to compile on gcc 5.4.0

Added missing doc link

Fixed line breaks

Fixed type issue on FreeBSD 10.3/64