Throw exception in i386 unwinders
    
    This patch changes i386 unwinders not to throw exceptions.
    
    gdb:
    
    2017-07-31  Yao Qi  <yao.qi@linaro.org>
    
    	* i386-tdep.c (i386_frame_cache) <base_p>: Remove.
    	(i386_alloc_frame_cache): Update.
    	(i386_frame_cache_1): Likewise.
    	(i386_frame_cache): Don't catch exceptions.
    	(i386_frame_this_id): Don't check cache->base_p.
    	(i386_frame_unwind_stop_reason): Likewise.
    	(i386_epilogue_frame_cache): Don't catch exceptions.
    	(i386_epilogue_frame_unwind_stop_reason): Don't check
    	cache->base_p.
    	(i386_epilogue_frame_this_id): Likewise.
    	(i386_sigtramp_frame_cache): Don't catch exceptions.
    	(i386_sigtramp_frame_unwind_stop_reason): Don't check
    	cache->base_p.
    	(i386_sigtramp_frame_this_id): Likewise.