toolchain-external/CodeSourcery MIPS 2015.05: fix lib-names headers

The CodeSourcery MIPS 2015.05 toolchain has some missing headers we need
to create manually in order to avoid compilation errors. A bug has been
already reported and fixed upstream, and the fix will be included in the
next release.

Fixes:
  http://autobuild.buildroot.net/results/bea/bea76392dec5c8e1bcea8be990ad109c6d27e947/
  http://autobuild.buildroot.net/results/64f/64f2b6b6e60d5c2d9537ad6891211cda6baaf6d5/


  ...and many more.

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>