btrace: identify cpu

btrace: identify cpu

Add a struct for identifying a processor and use it in linux-btrace.c when
identifying the processor we're running on.

We will need this feature for the new btrace format.

2015-02-09  Markus Metzger  <markus.t.metzger@intel.com>

	* common/btrace-common.h (btrace_cpu_vendor, btrace_cpu): New.
	* nat/linux-btrace.c: (btrace_this_cpu): New.
	(cpu_supports_bts): Call btrace_this_cpu.
	(intel_supports_bts): Add cpu parameter.