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

[OmniBlade]

Someone has ported the OMF support to a newer binutils and improved it at https://github.com/sillyc0n/binutils-gdb/tree/binutils-2_42-branch-omf-with-thread-support though I haven't tested it. Might be worth seeing if the upstream objects library that is being used is interested in adding omf support?

[OmniBlade]

Upstream repo looks like its https://github.com/gimli-rs/object though it was annoyingly hard to find given the generic name of the library?

[OmniBlade]

Added an upstream request at gimli-rs/object#736.