userdiff/perl: catch sub with brace on second line

userdiff/perl: catch sub with brace on second line

Accept

	sub foo
	{
	}

as an alternative to a more common style that introduces perl
functions with a brace on the first line (and likewise for BEGIN/END
blocks).  The new regex is a little hairy to avoid matching

	# forward declaration
	sub foo;

while continuing to match "sub foo($;@) {" and

	sub foo { # This routine is interesting;
		# in fact, the lines below explain how...

While at it, pay attention to Perl 5.14's "package foo {" syntax as an
alternative to the traditional "package foo;".

Requested-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>