1.1+18

CHANGES:

• Adding missing dependency on conf-c++ (#52 @dra27)

• Disable every warnings when compiling the vendored glpk code (#41 @kit-ty-kate @MisterDA)

• Replace sprintf and vsprintf with snprintf and vsnprintf (#41 @MisterDA)

• Always compile C++ files with -x c++ on non-msvc compilers to avoid issues when using clang (#53 @kit-ty-kate)