[ios64] - fixed offsets into the eventmem for arm64 - fixes bt keyboard cursor keys when compiled for arm64
Improved file buffering in CArchive.

CArchive already did some file buffering, but only on writes. Added the
equivalent code for reads. Also improved the write buffer case so that it
only ever issues sector-aligned writes (the read code does this from the
start). Shuffled various bits of code into the header file to squeeze a bit
more performance out of it.
[gui] auto height textboxes should take into account the cell height of the last row, which may be more than the lineheight for well-spaced fonts
[application] - remove m_bInBackground and its setter/getter and use
SetRenderGUI instead
[json] - fix jsonbuilder was not found when added to "PATH" from outside. Add the same approach like done in codegenerator.mk - fixes json generation when compiling from xcode
[airplay] - fix possible bad access as reported in http://issues.xbmc.org/main/issues/13
Merge pull request #4690 from jmarshallnz/auto_textbox_height_fix

[gui] auto height textboxes should take into account the cell height of last row
Merge pull request #4695 from Memphiz/badaccess

[airplay] - fix possible bad access as reported in
[airtunes] - phase out support for libshairport - its superseeded by libshairplay long enough on all platforms
Merge pull request #4248 from Memphiz/btcursorkeys64bit

[ios/arm64] - fix bt keyboard cursor keys when compiled for 64bit arm
settings: fix deserialization of list setting with empty default value
Merge pull request #4694 from Memphiz/fixjsongeneration

[json] - fix jsonbuilder was not found when added to "PATH" from outside...
Correct null check

Correct likely copy and paste mistake, and null check the correct
variable.

Fixes Coverity CID 1213840
Merge pull request #4234 from bavison/carchive_buffering

Improved file buffering in CArchive.
Merge pull request #4697 from Memphiz/phaseoutshairport

[airtunes] - phase out support for libshairport - its superseeded by lib...
Merge pull request #4693 from Memphiz/remove_background

[application] - remove m_bInBackground and its setter/getter and use
Merge pull request #4701 from cg110/CoverityFixes4

Fixes for the obvious bug from this weeks coverity scan.
videoplayer: adapt lateness detection and dropping to buffering
video player: present correct pts to user for a/v sync (after buffering in renderer)
videoplayer: some rework and documentation