cmake messages for user - ignore missing header messages, SC_BUILD_SCHEMA
silence MSVC warning
MSVC lacks stdbool.h
MSVC lacks nextafterf - add one from musl-libc with MIT license
changes for MSVC and nextafter, nextafterf
fix includes, most externs for windows
remove get_filename - won't work on windows
fix gcc warnings/errors in sc_nextafterf.c