package/kvazaar: needs C++ compiler

package/kvazaar: needs C++ compiler

Even if there is only one CPP file src/extras/crypto.cpp which should
be disabled by --without-cryptopp, kvazaar fail to build the shared
library libkvazaar.so when no C++ compiler is available.

checking whether we are using the GNU C++ compiler... no

Fixes:
[microblazel] http://autobuild.buildroot.net/results/5d1/5d140ed95e292f73b6770a5e5be717df844e4830
[arm] http://autobuild.buildroot.net/results/c55/c55b973502b9b88643ae9fca11447b547148275d

Signed-off-by: Romain Naour <romain.naour@smile.fr>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>