Fixes an issue where branches don't compile in the hybrid integrated
assembler because some jump instructions have not yet been integrated.
It does this by adding an instruction label for each corresponding
label generated by the standalone ARM assembler.

Note that in order to fix this, I had to change the signature of
virtual method Assembler::bindCfgNodeLabel to get the Cfg node (rather
than the index value). This allows the ARM hybrid assembler to
generate a label for each CfgNode (using the getAsmName() method).

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4334
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1407273006 .