Some escape sequence failures

[kddnewton]

assert_equal "\x13", "\c\x33"
assert_equal "\x13", "\C-\x33"
assert_equal "\xB3", "\M-\x33"

Right now all 3 of these are failing. It looks like \x sequences aren't being escaped with the flags.

# coding: US-ASCII
    assert_equal("\xe1", [0x00, 0xe1, 0xff].pack("C*")[/\M-a/])
    assert_equal("\xdc", [0x00, 0xdc, 0xff].pack("C*")[/\M-\\/])
    assert_equal("\x8a", [0x00, 0x8a, 0xff].pack("C*")[/\M-\n/])
    assert_equal("\x89", [0x00, 0x89, 0xff].pack("C*")[/\M-\t/])
    assert_equal("\x8d", [0x00, 0x8d, 0xff].pack("C*")[/\M-\r/])
    assert_equal("\x8c", [0x00, 0x8c, 0xff].pack("C*")[/\M-\f/])
    assert_equal("\x8b", [0x00, 0x8b, 0xff].pack("C*")[/\M-\v/])
    assert_equal("\x87", [0x00, 0x87, 0xff].pack("C*")[/\M-\a/])
    assert_equal("\x9b", [0x00, 0x9b, 0xff].pack("C*")[/\M-\e/])
    assert_equal("\x01", [0x00, 0x01, 0xff].pack("C*")[/\C-a/])

These are also failing for regexps.