Support OMF object format

[tomsons26]

Supporting OMF would also open objdiff to being used with Borland, really old MSVC, and Watcom targets There are probably a lot of other lesser used compilers that use OMF, probably everything very old aimed for dos uses OMF https://web.archive.org/web/20200207210113/https://pierrelib.pagesperso-orange.fr/exec_formats/OMF_v1.1.pdf is the specs OmniBlade had to do support for it in a binutils fork so decompme has a usable objdump https://github.com/OmniBlade/binutils-gdb/tree/omf-binutils-2_22-branch

another reference point can be https://github.com/tomsons26/objconv/commits/omf_fixes/ which is my fork that sort of fixes objconv to handle 32 bit OMF records properly, its a bit of a ugly hack tho as it can only output core c/cpp functions, it strips away inlines/comdats/anything compiler generated