Add a script 'check_headers_and_includes' to check that #include directives
are not against the grain.
Wrap this script together with 'check_makefile_consistency' into
'post_regtest_checks' and invoke that from the toplevel Makefile. So we can
easily add new checkers in the future.

Add a new make target 'post-regtest-checks' to just run those checks
and nothing else.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13570 a5019735-40e9-0310-863c-91ae7b9d1cf9
Fix two issues found by check_headers_and_includes.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13571 a5019735-40e9-0310-863c-91ae7b9d1cf9