_known_hosts_real: Pre-expand \t instead of relying on sed supporting it (Alioth: #314393).
dict: Trivial regex cleanup.
abook, kldunload: Pre-expand \t instead of relying on sed supporting it.
cc, c++: Install minimal completion for non-gcc ones (Alioth: #314417).
cc, c++: Check path to binary when finding out if it's gcc (Alioth: #314417).
f77, f95: Use the same completion as for g77, g95 if they are links to gfortran