CMake: Work around bug in FindQt4.cmake

Fixes: bug #694
CMake: Fix potential future cmake compat issue

Fixes CMP0054 warning with CMake 3.

See: bug #694
COPYING: Fix capitalization
arx-install-data: Fix whitespace/comment typos
audio: Add asserts for infinite vectors

We should really figure out the root cause here instead of checking them
at run-time.
audio: Fade out sources near the max distance

Otherwise some (loud) sources will abruptly start/stop as the player
moves towards/away from them. This problem could be reduced by setting a
higher max distance, but would still be technically there because the
inverse distance model never reaches zero gain. This may be realistic
but is undesirable if we want to cull distant sources.

This problem did not exist in vanilla AF - maybe our AL settings don't
exactly match the dsound falloff?
audio: Fix isReverbSupported() return on error
[style] Add missing brackets
[style] Add missing brackets
Fix assert of player.bag
[cppcheck] Remove unused std::ostringstream var
[cppcheck] Remove impossible if branch
[cppcheck] Remove ARX_CAST_TO_INT_THEN_FLOAT()

Was never used.
Simplify condition
[cppcheck] Remove redundant nullptr check
Use original pointer when moving ownership

This makes it clearer that we are transferring ownership of the spell
object and not just passing a temporary pointer to it. Also might
fix a false positive cppcheck warning.
[cppcheck] Fix local variable aliasing
[cppcheck] Remove redundant nullptr check
[cppcheck] Change variable to bool
[cppcheck] Remove unused variable