libstdc++: Fix Darwin bootstrap by simplifying ver file syntax.

libstdc++: Fix Darwin bootstrap by simplifying ver file syntax.

The symbol parsing script does not handle the closing brace of a new
symbol group and the identifier for the inherited group to be on
different lines, which r16-1708-gaf5b72cf9f564 introduced. Fixed by
making the conditional encompass both the brace and the identifier.

libstdc++-v3/ChangeLog:

	* config/abi/pre/gnu.ver: Keep the closing brace of the
	CXXABI_1.3.17 symbol group together with the identifier
	for the inherited group.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>