NEVERHOOD: Remove NRect constructor

Otherwise, every global variable of type NRect requires a constructor to be
run, which can cause portability issue.
GUI: Use Domain::const_iterator in EventRecorder code when possible.
COMMON: Do not let ConfigManager::Domain inherit from StringMap.

Instead we provide wrapper functionality now. Intuitively a Domain is not a
simple StringMap.
GRAPHICS: Fix VectorRendererSpec for RGBA8888.

Formerly values in the gradient and blending code overflowed and thus caused
incorrect colors. Now there's some special case for 32bpp modes, which needs
slightly more operations but assures a correct output.
GRAPHICS: Add error-checking in blendPixelPtr for invalid BPPs
GRAPHICS: Fix fonts/bdf.cpp to allow for 32bpp to be used
GUI: Allow GUI cursor creation to work with abitrary 2/4Bpp formats.
GUI: Change name of GUI-renderers to remove "16-bit"
GRAPHICS: Allow VectorRenderer and ThemeEngine to init with 4BPP
COMMON: Rename ConfigFile to INIFile.

This clears up that 'ConfigFile' is actually a class handling only INI-files.
COMMON: Remove outdated comments on INIFile.

These very old comments claimed that ConfigManager uses INIFile. This is not
true however. Thus removing them should clear things up a little bit.
COMMON: Remove commented out include in config-manager.h.
Merge pull request #373 from lordhoto/ini-file

Rename ConfigFile to INIFile and remove outdated comments
Merge pull request #369 from fingolfin/fix-neverhood

NEVERHOOD: Remove NRect constructor
WINTERMUTE: Avoid setting alpha-image when filename is ""
WINTERMUTE: Fix uninitialized scalar field (CID1060922)
MORTEVIELLE: Use more accurate frequency for music
MORTEVIELLE: Play ambiant sounds
MORTEVIELLE: some refactoring in ambiant sound code
MORTEVIELLE: Handle sounds