[arm] compute framereg and framesize when needed

I find local variables framereg and framesize is only used when cache
isn't NULL.  This patch to move the code into "if (cache)" block.

gdb:

2014-11-29  Yao Qi  <yao@codesourcery.com>

	* arm-tdep.c (arm_analyze_prologue): Move local variables
	'framereg' and 'framesize' to inner block.  Move code to
	inner block too.
Check that thread stack temps are not already enabled before enabling them.

This fixes a regression introduced by 6c659fc2c7cd2da6d2b9a3d7c38597ad3821832a.

gdb/ChangeLog:

	* eval.c (evaluate_subexp): Check that thread stack temporaries
	are not already enabled before enabling them.
Automatic date update in version.in