GeanyLua: Support for LuaJIT and Lua 5.1-5.4

[xiota]

Extends #1233 to add support for Lua 5.1 and LuaJIT by adding compatibility functions/defines. The build script is fixed to not ignore the --with-lua-pkg option and to recognize Lua variants: lua51, luajit, lua, lua53, lua52. Systems that use a different basename will have to explicitly specify the name, eg lua5.1 or lua-5.1, during configure. To change variants, reconfigure and rebuild.

./configure --with-lua-pkg=[lua]
make -C geanylua clean
make -C geanylua

Supercedes #1231, #1233, #1235.
Resolves #1228. Resolves #1133.

[techee]

I'm not sure we should do that. If the decision is to use LuaJIT with a Lua 5.1 fallback, we should support just these versions. Supporting tons of lua versions each with slight language modifications could really become hard to maintain. I don't think anyone of us will have time to test the plugin against all of the lua libraries. Similarly, if we decide to switch to say Lua 5.4, we should stop supporting other Lua versions.

Plus I think you accidentally pushed about all the changes in geany-plugins you've been playing with ;-)

[Skif-off]

@techee
In fact, there are few changes (I don't understand why changes not related to GeanyLua are lumped together) and these versions of Lua will no longer be different.
So theoretically, support will not be required for a long time.

[xiota]

Rebased on master. So far, when switching between Lua versions, including LuaJIT, the only issues I've run into were not isolated to one version of Lua.