Shortened the name a bit and made it clearer.
Shortened the function version a bit.
Added a ADD_SUFFX macro.
Removed standard-checking macros, because most compilers don't care about them anyway and probably will let you use that feature even without explicitly asking for C11.
Improved the definition of WRONG_TYPE.
Improved the documentation a bit.
Changed the default of ADD_SUFFIX to the number itself.
Corrected the concatenation symbols in ADD_SUFFIX.
Accidentally forgot to add a ',' at the end of some lines in ADD_SUFFIX.
Prettyfied the generic version of COMPARE_FLOATS and made it easier to read.
Fixed the message in WRONG_TYPE macro.
Made the functions prettyier and easier to read too.
Made the functions static inlines.