Fix tight loop on recursively-defined symbols

Fix tight loop on recursively-defined symbols

This patch fixes a bug in GAS where the assembler enters a tight loop
when attempting to resolve recursively-defined symbols, e.g. when
trying to assemble "a=a".

This is a regression introduced between binutils 2.32 and 2.33,
by commit 1903f1385bff9

	* symbols.c (struct local_symbol): Update comment.
	(resolve_symbol_value): For resolved symbols equated to other
	symbols, verify that the referenced symbol is not a local_symbol
	before accessing sy_value.  Don't leave symbol loops during
	finalize_syms resolution.
	* testsuite/gas/all/assign-bad-recursive.d: New test.
	* testsuite/gas/all/assign-bad-recursive.l: Error output for test.
	* testsuite/gas/all/assign-bad-recursive.s: Assembly for test.
	* testsuite/gas/all/gas.exp: Run it.

(cherry picked from commit 2a50b401465f74d7f3ee1654915b9070b4dc0fee)