Separate compiler warnings for C and C++
Separate compiler warnings for C and C++

Avoids compiler whining about C++ warning options when compiling C files.

vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa