toolchain: add glibc menu option for (custom) version

(E)GLIBC version numbers can be set in the menu and used through the variables BR2_TOOLCHAIN_BUILDROOT_GLIBC_VERSION and BR2_TOOLCHAIN_BUILDROOT_EGLIBC_VERSION
glibc: use glibc menu variables and support version 2.13

GLIBC_VERSION is set to BR2_TOOLCHAIN_BUILDROOT_GLIBC_VERSION or BR2_TOOLCHAIN_BUILDROOT_EGLIBC_VERSION for glibc and eglibc builds; a glibc 2.13 build is added for linux host builds
configs: support X86 host build for the qapitrace GUI

qapitrace runs (typically) remotely on a host; a linux x86_64 build has been (partially) verified on Debian Wheezy
icu: correctly use minimal icu data set
glibc: unescape version string
qt5webkit: GStreamer DRAIN query support in the video sink

When the sink receives a DRAIN query, clean up the buffers it handles
and signal the player to do the same.

This patch also introduce a change in the player video frame painting
logic, if the video texture update fails then schedule another
repaint, unless the EOS message was received.
Merge pull request #19 from Metrological/gst-drain

qt5webkit: GStreamer DRAIN query support in the video sink
qtbrowser: use version 1.0.1
qt5base: CMake should not depend on OpenGL with -no-opengl

define an OpenGL scope by testing Qt's configuration
apitrace : enable GUI build for Qt5

qapitrace builds with more recent versions of Qt
configs: bump GUI build to Qt5

Qt4 based builds are no longer supported
qt5webkit: make 'discovery' and 'accelerated canvas' configurable

instead of 'always on' the options can now be disabled
qt5webkit: correct .mk to use configurable options
qt5webkit: correct .mk, add  options to WEBKIT_CONFIG
qt5webkit: disable 'accelerated canvas' in non-OpenGL builds
rpi-userland: bump to latest version
rpi-firmware: bump to latest version
rpi: bump to kernel 3.10.36
qtbrowser: bump to version 1.0.4
rpi-firmware: bump to latest version