Increase the ccache size on travis from 100M to 150M as we've probably passed...

Increase the ccache size on travis from 100M to 150M as we've probably passed the limit already with all the tests that we have now.

.travis.yml

@@ -39,7 +39,7 @@ env:
     - USE_CCACHE=1
     - CCACHE_SLOPPINESS=pch_defines,time_macros
     - CCACHE_COMPRESS=1
-    - CCACHE_MAXSIZE=100M
+    - CCACHE_MAXSIZE=150M
     - PATH="/usr/lib/ccache:$HOME/gcc-symlinks:$PATH"
   matrix:
     - BACKEND=c