checkpatch: enforce sane perl version

checkpatch: enforce sane perl version

I got a bug report from a couple of users who said checkpatch.pl was
broken for them.  It was erroring out on fairly random lines most commonly
with messages like:

	Nested quantifiers in regex; marked by <--HERE in m/(\((?:[^\(\)]++ <-- HERE |(?-1))*\))/ at ./checkpatch.pl line 340.

The bug reporter was running a version of perl 5.8 which was end-of-lifed
in 2008: http://www.cpan.org/src/.  Versions of perl this old are at
_best_ quite untested.  At worst, they are crusty and known to be
completely broken.

If folks have a system _that_ old, then we should have mercy on them and
give them a half-decent error message rather than fail with nutty error
messages.

This patch enforces that checkpatch.pl is run with perl 5.10, which was
end-of-lifed in 2009.  The new --ignore-perl-version command-line switch
will let folks override this if they want.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>