Remove m4/fontforge_compiler_flags.m4 and do it in configure.ac

Program simplification by moving AX_CHECK_COMPILE_FLAG() into configure.ac
to make it easier to follow program logic.
remove line between "#ifndef _FF_CONFIG_H" and "#define _FF_CONFIG_H 1"
Delete m4/fontforge_my_flags_and_libs.m4 for simplification's sake

Move away from mental gymnastics of having to look in other files for
info and simply put these variables where configure.ac makes use of them.
Merge pull request #965 from JoesCat/master

Remove some files calling other files.