fix missing gcc include dir and move lvm-config.1
    
    - build with gcc/g++ even if clang is installed
    - bring back configuration for gcc arch include dir (Yury Zaytsev, #893817)
      which was dropped in 3.0-0.1.rc3
    - BR gcc and gcc-c++ and Require gcc with gcc_version
    - move lvm-config manpage to devel subpackage (#855882)