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.

gdb/common/btrace-common.h

@@ -61,6 +61,34 @@ enum btrace_format
   BTRACE_FORMAT_BTS
 };
 
+/* An enumeration of cpu vendors.  */
+
+enum btrace_cpu_vendor
+{
+  /* We do not know this vendor.  */
+  CV_UNKNOWN,
+
+  /* Intel.  */
+  CV_INTEL
+};
+
+/* A cpu identifier.  */
+
+struct btrace_cpu
+{
+  /* The processor vendor.  */
+  enum btrace_cpu_vendor vendor;
+
+  /* The cpu family.  */
+  unsigned short family;
+
+  /* The cpu model.  */
+  unsigned char model;
+
+  /* The cpu stepping.  */
+  unsigned char stepping;
+};
+
 /* A BTS configuration.  */
 
 struct btrace_config_bts