Manual cleanup of cmake code:

Removed unused file cmake/cat.cmake
Removed undocumented/useless file scripts/mysql_config.pl.in
Renamed: scripts/mysqld_multi.sh -> scripts/mysqld_multi.pl.in
Renamed: scripts/mysqldumpslow.sh -> scripts/mysqldumpslow.pl.in

Remove attempt to install libgcc.a
Misc cosmetics.

Change-Id: Idec937ace73e8b5eb69222987721b0f03378e6fe