Add signature support to eclmaps

[DankRank]

In #17 I introduced support for instruction menmonic mappings. I also intended signatures to be definable by user.

What I plan to do:

• ~~better argument parsing, so that multiple eclmaps can be loaded~~ done in #42
• conversion of internal mappings to eclmaps
• a flag to disable internal mappigns
• checking for correctness of signatures

[ManDude]

cool but at least accept #39 meanwhile. :tannedcirno:

[DankRank]

@ManDude don't you have push access? :thonk:

[nmlgc]

He actually didn't, my bad. Sent out the invitation.