add an exists() method to FilePackageManager

also replace the handwritten case-convert with boost::algorthm::to_lower
improve findTexture

use STL replace and boost::algo::to_lower
also whenever searching for a .avi file, also check .ogg
fix files not being found in the standard package (i.e. not .fbz)

Folder names are lower case here, to fix that just check both normal
and lower case
Revert "improve findTexture"

This reverts commit 8ff7f74b20a92ba996f848ae12292332e423bf08.
Revert "add an exists() method to FilePackageManager"

This reverts commit d954558dc7f27d055b1d726f71cf0de191a62909.

Conflicts:
	filesystem/standard_package.cpp
build hotfix: gcc hangs on GameWorldFold.cpp
memory leaks: vasprintf in Logger.

allocations are a little bit expensive for logger
minor: missing data files shouldn't be logged to file in final release build
CombatWindow dtor fix: window should be destroyed after radar (double free)
fixed compilation on OS X