Test empty captures in p5regex.

Includes a failing test for when one is at the start, which breaks
scanning.

Author: jnthn

t/p5regex/rx_captures

@@ -2,6 +2,9 @@
 (a.)..(..)		zzzabcdefzzz	<mob: abcdef @ 3>	basic $0
 (a.)..(..)		zzzabcdefzzz	<mob[0]: ab @ 3>	basic $1
 (a.)..(..)		zzzabcdefzzz	<mob[1]: ef @ 7>	basic $2
+d()ef		zzzabcdefzzz	y			empty capture
+# todo :pge<bug>
+()ef		zzzabcdefzzz	y			empty capture at start
 (a(b(c))(d))		abcd		y			nested match
 (a(b(c))(d))		abcd		<mob: abcd @ 0>		nested match
 (a(b(c))(d))		abcd		<mob[0]: abcd @ 0>	nested match