Two refactors: move summary common code; stop overusing 'perl'

Move much of the common setup done by all (non-JSON) summarizers out to
a separate module, and just use it from the various summary routines.

Also stop overusing 'perl' where I really mean 'compiler'.  Not only is
it confusing now, it will get much worse if I ever add non-Perl-family
languages to the compiler suite.

Author: Geoffrey Broadwell