Form/DataField/Angle: Add option to enable fine adjustment of values
Dialogs/Task/SectorZoneEditWidget: Enable fine adjustments of radials

Implements trac request #2540.
Form/DataField/Angle: Fix rounding issues on angles.

Due to rounding issues a 360° was sometimes present in
the ComboBox leading to an assertion on selection.
Prevent this issue by enforcing the range 0 - 359 for values.
LX1600: Fixed API documentation
SDL/Bitmap: Fixed indentation
Screen/Point: Added GetCenter() method
DigitEntry: Call assert() before using the checked variables
DigitEntry: Added API documentation
FontEdit: Made "Bold" and "Italic" translatable
Config/Registry: Applied naming convention
Fonts: Renamed FontHeight variable to font_height
Device/device: Use unsigned for iterating
InterfaceConfigPanel: Used StringIsEqual() instead of _tcscmp()
LanguageGlue: Applied naming convention
LanguageGlue: Used StringIsEqual() instead of _tcscmp()
InterfaceConfigPanel: Don't translate "English" as language name

If the automatic language detection fails we should offer the option
"English" instead of "English" in a language that the user can't read.
LanguageGlue: Added language names to BuiltinLanguage struct
LX1600: Added SetTimeOffset() function
LX1600: Added SetSmartDiffFilter() function
LX1600: Added SetVarioSettings() function