openjpeg: fix build without C++ support

openjpeg: fix build without C++ support

Fixes:
http://autobuild.buildroot.net/results/e2f/e2ff0a7fa2b911157edf6c43a8eed797b22edd46/
http://autobuild.buildroot.net/results/670/6706339e7df2f2e7d0d7a15663bed185ca55c2a1/

Openjpeg is written in C, but with the move to CMake the build system now
errors out if a C++ compiler isn't available.  Fix it by patching the
CMakeLists.txt to not require C++ support.

Patch submitted upstream:
https://github.com/uclouvain/openjpeg/pull/1027

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>