perlcc: update to 2.15 from master

-f passthru
better --version
better spawn: waitpid check error code
add --dryrun
less default noisyness
Create revision at Makefile.PL EUMM WriteMakefile.
Tested ok on Win32 without git

Skip installing 5.16 and higher.

Fixed conflicts:
	Makefile.PL
	script/perlcc.PL
#117: need to write B::C::Flags earlier to be parsed by libscan, and installed

See https://travis-ci.org/rurban/perl-compiler/jobs/4519819 for a typical failure.
Cant locate B/C/Flags.pm in @INC