allow selective definition of internal sound catalogs
get sound by depth
add ambient sound effects to battlescape

defined by terrain type.
adjust bubbles when aiming.
use different sprite sheet for underwater bullets
fix reorder, remove unused variables from Globe
Merge pull request #939 from ajschult/Globe-compile

fix reorder, remove unused variables from Globe
weapons that don't work on land
else*
Added xBRZ scaler.
Some more GLSL shaders for good measure.
Fix.
Fixx
Fixxx
more melee for aliens

units may now have a built in melee weapon that doesn't occupy a slot,
as defined in the unit section of the ruleset under the tag "meleeWeapon:"
with an accompanying string referring to an item.

this is only available to the AI, and as such some adjustments have taken
place to make aliens decide which to use, given their current situation,
as per original TFTD.

units can have a list of items that are "built in", and these items will
be given to the unit automatically. additionally, fixed weapons and alien
weapons can now be allocated to the left hand, meaning HWPs can have
secondary weapon systems installed.
whoops
Merge remote-tracking branch 'supsuperorgin/master' into OpenXcomExtended

Conflicts:
	src/Ruleset/RuleItem.cpp
	src/Ruleset/RuleItem.h