Fix T37777: layout.column_flow() not working correct with retina / DPI.
Attempt to fix compilation against libav-0.8.9
More updates, fixes and cleanup to install_deps.sh.

So, after hours of wild hunt, I think both CMake and Scons builds work again.
There were several small issues hiding here and there, esp. for scons.

*WARNING* the --all-static is currently officially broken (it was already quite useless in fact).
          I’m seriously considering dropping it completely, having a script compiling a chain
          of static libs in a complete working way for *two* different build systems is just
          too much work (static libs are *really* a nightmare at link time).

Builders who want to generate static Blender (to share it e.g.) will have to handle things by hand for now.

Main other points changed:

* Many changes to generated settings for scons (notably, I had to hack around the fact that the short ld -l
  option does not work with lib names like 'Iex-2_1', which is not that surprising).
* Opencollada remains the only lib built statically (can't get it to build dyn currently).
* All other libs, even ILMBase ones, are now fully dynamic ones.
* Some general cleanup with CMake definitions of built libs.
* Git-libs do not clone again and again the repo anymore!
Add meaningful default for SimpleDeform modifier's angle prop.
Code Cleanup: replace global debug checks in raycast with DEBUG ifdef
Fix T37780: no languages in user preferences with SCons on Windows / Linux.

The "languages" file was not copied, probably this was not noticed earlier
because it only affects clean builds.
Fix T37769: inconsistent behavior of Remove Selected From Active Group.

Add Selected to Active Group presented a menu with groups to choose from, while
this seemingly inverse operation did not and used all groups of the active
object.

Now both operators present a menu, with as first option "All Groups".
Code Cleanup: move mesh mapping functions into their own file/header
Mesh API: Add BKE_mesh_origindex_map_create

This API function lets original data loop over its derived data,
Use for vertex paint, replacing custom function.
Code cleanup: indent preprocessor directives inside #ifdef
Use factor subtype for plane track opacity
Fix for off by one error noted by Anthony Edlin
Fix T37757: MCE - Mask Pivot Point individual origins doesnt work

Simple wasn't implemented.
RNA: Add assert to ensure the idprop is correct size on array get/set
Add libxml2, libyaml-cpp and libtinyxml to default dependencies (always-installed packages), looks like they are needed...
Attempt to fix compilation error on Debian armel kernel
Fix T37786: Curves: Geometry tab is missing

Was broken by rB2a55d68e1927 which inverted condition
in poll function for Geometry panel.
Code Cleanup: use const's and bools for idprops
Fix T37595: Switching modal transform broke with trackball rotation.

Id properties may have different sized "values" array depending on the
transform operator