improve x86 codegen support for blockaddress. We now compile

the testcase into:

_test1:                                                     ## @test1
## BB#0:                                                    ## %entry
	leaq	L_test1_bb6(%rip), %rax
	jmpq	*%rax
L_test1_bb:                                                 ## Address Taken
LBB1_1:                                                     ## %bb
	movb	$1, %al
	ret
L_test1_bb6:                                                ## Address Taken
LBB1_2:                                                     ## %bb6
	movb	$2, %al
	ret

Note, it is very very strange that BlockAddressSDNode doesn't carry 
around TargetFlags.  Dan, please fix this.

llvm-svn: 85703