vdr-plugin-text2skin

Changes:

- Fix build with ImageMagick >= 6.6.2 (thanks to Anssi Hannula / closes #409)
- Documentation spelling fixes.
- Added experimental RELAX NG schema for skin XML files.
- Set minimum value of bitmap cache size in menu to 1.
- Fix bitmap cache size initialization when built with gcc 4.6.
- Update epgsearch recording search timer name parsing for epgsearch >= 0.9.21.
- Warning and code cleanups.