t/xs.t to skip some if futile.
t/xs.t to test PERL="perl -w" exercising space-quoting.
Enable PERL=>"$^X -Iinc" to work again.
Merge pull request #150 from mohawk2/perlmacrospace

Enable PERL=>"$^X -Iinc" to work again.
Simulate Module::Install $(PERL) changing.
Invert logic to avoid "unless/else".
Handle Module::Install $(PERL) Makefile editing.
Merge pull request #151 from mohawk2/perlmacro-modinstall

Handle Module::Install $(PERL) Makefile editing.
Release engineering for v6.99_10
increase readability of MakeMaker::flush()
write Makefile.pm
helper subs
ppd
metafile_target
tool_autosplit
distmeta_target
distsignature_target
pm_to_blib
clean_subdirs_target
realclean_subdirs_target