Merge topic 'empty-compiler-crash'

ccfeefa Fix crash on empty CMAKE_<lang>_COMPILER value (#13901)
Merge topic 'CPackRPM-fixSomeRPMSpecificVarHandling'

9be3da1 CPackRPM fix #13898 uses IF(DEFINED var) to avoid wrong var value logic
Merge topic 'UseMakefileHeaderExtensions'

27e14a8 automoc: use the header extensions from cmMakefile
10511aa automoc: use a std::vector<> instead a std::list
Merge topic 'EclipseDetectClangIncludeDirs'

a396b6e Eclipse: also detect include dirs and macro for clang (#13823)
Merge branch 'master' into next