Expose mapheader_t's selectheading option to Lua

This merge request exposes the mapheader_t's selectheading option to Lua. This merge request is required for MR !1239 (closed).

Test files: srb2_exposeselectheadingtest.exe exposeselectheadingtest.lua

mentioned in merge request !1239 (closed)

changed the description

added 10 commits

• d0955179...4ab667c6 - 9 commits from branch STJr:next
• 0280721f - Merge branch 'next' of https://git.do.srb2.org/STJr/SRB2 into expose-selectheading

Compare with previous version

changed the description

added 6 commits

• 0280721f...ecb33351 - 5 commits from branch STJr:next
• 51d52f73 - Merge branch 'next' of https://git.do.srb2.org/STJr/SRB2 into expose-selectheading

Compare with previous version

changed the description

Should I expose Playing() in this merge request or a different one?

I don't think we need to expose that at the moment.

added 11 commits

• 51d52f73...d004515d - 10 commits from branch STJr:next
• 7fde15d0 - Merge branch 'next' of https://git.do.srb2.org/STJr/SRB2 into expose-selectheading

Compare with previous version

changed the description

While I don't have time to test this as extensively as I would like, everything appears to work as advertised. I am actually elated that someone took the time to turn my idea into a checklist of features, and the scope of what this allows -- mapheader, linedef, and mapthing editing -- leaves me really impressed!

I'm giving this a thumbs up. However, I would like to make note of the technicalities of modifying certain map info in netgames. From my own tests, I've confirmed that mapheader, linedef, sector, and thing properties are not carried over into the gamestate. For basic or linear modification through MapHeader, this won't be much of an issue, but any dynamic modification done through this hook will have to be stored in some way and sent through NetVars in order to ensure that all joining clients are applying the appropriate changes. Mapheader_t is also a userdata table, and so any changes made to it will be persistent throughout runtime. This does not affect the viability of certain usages of this hook, it only means that we should advise users of the nuances of using these features once they are merged.

Edit: posted in the wrong thread, but most everything still applies

merged

mentioned in commit 77c51c62