Expose part of Guild API to Script Engine

This adds two new functions to script engine: getguildinfo() and getguildmembers().

They work similar to the party counterparts, and have the same deprecated behavior of using $@variables which force you to use copyarray.

General Note: Should I rename getguildmembers() to getguildmember() for consistency with getpartymember()?

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Note for @WildX : Should we add the "lame" hack function which allows script engine to modify guild roles; Or you prefer to wait until this gets supported by ManaPlus?

Guild alliances and roles are entirely exposed to ManaPlus and used in game mechanics (hostility, EXP tax, etc.) - But ManaPlus still doesn't allows changing it.

Allowing the script engine to change these in ManaPlus' stead is possible but do we want that?

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Note for @gumiko / @4144 : I have no idea where I saw it and couldn't find again, but I'm sure either you, 4144, or someone else on Hercules wanted to convert getpartymember() to don't use $@variables anymore, and output them to script (or with a more restricted scope).

Reducing scope is always a good idea but I see no reason to don't commit with a scope bigger than needed and reduce it later (unless you can affirm that it'll be changed in the next 18 days or change this yourself. Using $@ is both the more consistent as the best I can do right now).

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**Depends on !16 (merged) **