DVDSubtitleStream: better detect stream encoding and optimization
Use BOM detection for all supported charsets, not only UTF-8 and UTF-16LE
Do not double convert subtitle->wstring->UTF-8. Use direct conversion subtitle->UTF-8
additionally: CharsetConverter: subtitleCharsetToW -> subtitleCharsetToUtf8
[spectrum] cosmetic: Use static where appropriate
[rbp] Remove PiAudio engine
[rbp] Add PiAudio sink
[spectrum] Draw spectrum as a single object

glDrawElements is called 256 times per frame, once for each bar. It is more efficient to batch up larger blocks.
This change draws the specrum with a single glDrawElements call.

Looking at visualisation in full screen mode, it used to top out at 75 fps. With this PR it can hit 125 fps.
fixed: add GIF as known header to cximage.
changed: pass detected image mimetype further down to avoid a second lookup.
imagefactory: removed unused method.
Support uClibc compilation

partly based on aports from Alpine Linux:
http://code.ohloh.net/file?fid=Up3lAbVglPtyupfNPazFHQYMKM8&cid=Sr-nRbkkE8E&s=&fp=302485&mp=&projSelected=true#L0
[epg] handle <onback> just like every other control
[pvr] no need to handle ACTION_NAV_BACK and ACTION_PREVIOUS_MENU in GUIWindowPVRCommon - they're handled in GUIMediaWindow already
changed: added another GetMimeType for urls and use it in the imagefactory if no mimetype is set.
[pvr] only handle ACTION_NAV_BACK in GUIWindowPVRRecordings if there's a parent directory to go to, else drop down to the base class as the action will be handled by the window system
[info] don't URL decode paths and filenames - pass them as-is (save user/pass detail). Fixes #13823
[masterlock] check master lock when going to the skin settings window. Closes #14070
Merge pull request #3947 from wsoltys/imagemimetype

fixed: loading of images from urls which don't have an extension...
Merge pull request #3961 from jmarshallnz/check_masterlock_skin_settings

[masterlock] check master lock when going to the skin settings window.
Merge pull request #3960 from jmarshallnz/no_decode_paths

[info] don't URL decode paths and filenames - pass them as-is (save user/pass)
Various minor settings level adjustments to settings.xml

As discussed on the internal Team XBMC forum thread here: http://forum.xbmc.org/showthread.php?tid=163982

Various non-controversal level adjustments for various settings.
videoplayer.useframemtdec 2 -> 3

change level of videoplayer.useframemtdec (Frame Multi Thread Decoding) as requested by fritsch