tfile: Don't infer the PC from the tracepoint if the PC is a pseudo-register.

tfile: Don't infer the PC from the tracepoint if the PC is a pseudo-register.

This PC guessing can't work when the PC is a pseudo-register.
Pseudo-register values don't end up stored in the regcache, they're
always recomputed.  And, it's actually wrong to try to write a
pseudo-register with regcache_raw_supply.  Skip it and add a comment.

gdb/
2014-01-13  Pedro Alves  <palves@redhat.com>

	* tracepoint.c (tfile_fetch_registers): Don't infer the PC from
	the tracepoint if the PC is a pseudo-register.