Rename files to 8.3 for DOS builds

[philburk]

DOS cannot handle long filenames.

Updated all Makefiles and CMakeLists.txt to reflect the changes.

Special thanks to https://github.com/guberathome for providing scripts to do the conversion. See #201

The original and new file names are:

csrc/pf_io_none.c                   csrc/ionone.c
csrc/posix/pf_io_posix.c            csrc/posix/ioposix.c
csrc/stdio/pf_fileio_stdio.c        csrc/stdio/fiostdio.c
csrc/stdio/pf_io_stdio.c            csrc/stdio/iostdio.c
csrc/win32/pf_io_win32.c            csrc/win32/iowin32.c
csrc/win32_console/pf_io_win32_console.c csrc/win32csl/iowin32c.c
fth/save-input.fth                  fth/savinput.fth
fth/structure.fth                   fth/structur.fth
fth/t_include.fth                   fth/tinclude.fth
fth/t_load_defer.fth                fth/tlddefer.fth
fth/t_load_pairs.fth                fth/tldpairs.fth
fth/t_load_semi.fth                 fth/tldsemi.fth
fth/t_load_undef.fth                fth/tldundef.fth
fth/t_required_helper1.fth          fth/treqhlp1.fth
fth/t_required_helper2.fth          fth/treqhlp2.fth
fth/t_strings.fth                   fth/tstrings.fth
fth/utils/dump_struct.fth           fth/utils/dumpstru.fth
fth/utils/load_file.fth             fth/utils/loadfile.fth
fth/utils/make_all256.fth           fth/utils/make_all.fth

Note that the folder "csrc/win32_console" became "csrc/win32csl".

Fixes #216