d-demangle.c (dlang_attributes): Handle return attributes, ignoring return parameters...

d-demangle.c (dlang_attributes): Handle return attributes, ignoring return parameters in the mangled string.

libiberty/ChangeLog:

2015-05-16  Iain Buclaw  <ibuclaw@gdcproject.org>

	* d-demangle.c (dlang_attributes): Handle return attributes, ignoring
	return parameters in the mangled string.  Return NULL if have encountered
	an unknown attribute.
	(dlang_function_args): Handle return parameters in the mangled string.
	* testsuite/d-demangle-expected: Add coverage tests for functions with
	return parameters and return attributes.

From-SVN: r223244