upgrade 3rdparty software build system for Xcode 4.5

change details
- update base SDK versions in build-env.sh
- build-env.sh now uses xcode-select instead of hardcoding the
  platforms base path
- adjust Mac OS X platform settings in build-env.sh because in Xcode 4.5
  this platform is no longer specially treated and is now supported in the
  same way as the iPhone and simulator platforms
3rdparty software build: platform builds can now be enabled/disabled individually

change details
- platform builds are enabled/disabled in build-env.sh
- the Mac OS X build is disabled by default
3rdparty software build: better check for presence of autoconf/automake in Fuego build script
3rdparty software build: improve docs + fix some exit code handling in framework script build-software.sh
3rdparty software build: update comments in build-env.sh to reflect directory structure that results from xcode-select
3rdparty software build: build-quincykit.sh overwrites result of previous build
update Xcode project reference to book.dat to SDK version 6.0
Merge branch 'upgrade-to-xcode-4.5' into develop
add wooden background

the image files have been made from this texture [1]. on 18 January 2013
I have sent an email to psdgraphics@yahoo.com, asking for "non-profit use"
permission. I have not received an answer, which according to the notes
on this page [2] implies that it is OK to use the image (the author says
that "I will not reply unless something is not OK").

[1] http://www.psdgraphics.com/backgrounds/light-wooden-background/
[2] http://www.psdgraphics.com/about/terms-of-use/