MIPS16e2: Add MIPS16e2 ASE GAS test infrastructure

Define a new 32-bit and 64-bit MIPS16e2 test architecture and adjust
existing tests now run against these architectures accordingly.

	gas/
	* testsuite/gas/mips/mips.exp (run_dump_test_arch): Add
	`mips16e2@' prefix.
	(run_list_test_arch): Likewise.
	(mips16e2-32, mips16e2-64): New architectures.
	* testsuite/gas/mips/mips16e2-32@mips16-macro.d: New test.
	* testsuite/gas/mips/mips16e2-32@mips16-macro-t.d: New test.
	* testsuite/gas/mips/mips16e2-32@mips16-macro-e.d: New test.
	* testsuite/gas/mips/mips16e2-32@mips16-insn-t.d: New test.
	* testsuite/gas/mips/mips16e2-32@mips16-insn-e.d: New test.
	* testsuite/gas/mips/mips16e2-32@mips16e-64.d: New test.
	* testsuite/gas/mips/mips16e2-32@mips16-sub.d: New test.
	* testsuite/gas/mips/mips16e2-32@mips16e-64-sub.d: New test.
	* testsuite/gas/mips/mips16e2@relax-swap3.d: New test.
	* testsuite/gas/mips/mips16-32@mips16-asmacro.d: Remove `source'
	tag.  Add `-I$srcdir/$subdir' to `as' flags.
	* testsuite/gas/mips/mips16-64@mips16-asmacro.d: Likewise.
	* testsuite/gas/mips/mips16e2-32@mips16-macro.l: New stderr
	output.
	* testsuite/gas/mips/mips16e2-32@mips16-macro-t.l: New stderr
	output.
	* testsuite/gas/mips/mips16e2-32@mips16-macro-e.l: New stderr
	output.
	* testsuite/gas/mips/mips16e2-32@mips16-insn-t.l: New stderr
	output.
	* testsuite/gas/mips/mips16e2-32@mips16-insn-e.l: New stderr
	output.
	* testsuite/gas/mips/mips16-sub.s: Add `.set nomips16e2'.
	* testsuite/gas/mips/mips16e-sub.s: Likewise.
	* testsuite/gas/mips/mips16e-64-sub.s: Likewise.
	* testsuite/gas/mips/mips16-asmacro.s: Remove `.set mips32'.
	* testsuite/gas/mips/mips16-32@mips16-asmacro.s: New test
	source.
	* testsuite/gas/mips/mips16-64@mips16-asmacro.s: New test
	source.