Update of version and changelog for release-0.29.0
Fixup of a problem in Matrix's test case
Updated example requirements
Fixup of a problem with Submatrix(Matrix) on clang
Fixup in the build system

- Fixed the detection of GL version and extensions that
  failed on windows.
- Updated the configure.py script to ignore if the build
  directory cannot be completelly removed.
Minor fixup in the build system

- If the GLX example harness is used then pthread is linked to it.
Merge branch 'release-0.29.0' into develop