Continuing through my pile of testsuite problems found while working on 
cleaning up nios2 test results....

I found that the results for the gdb.trace tests were really messy on 
targets that don't support the trace features.  The trouble affected 
various other embedded targets I tried, not just nios2.  Specific 
problems included:

* The header file trace-common.h that is used by most of the test 
programs in this directory causes multiple compilation errors (not just 
the obvious preprocessor #error) on architectures it doesn't know about, 
and the checks in the .exp files for successful compilation of the test 
case didn't distinguish between failures for missing arch support 
(should have "unsupported" status) and failures due to unknown causes 
(should be "untested").  My understanding is that adding arch support to 
trace-common.h won't do anything useful without implementing the 
underlying fast tracepoint support too.

* Several test cases depend on linking with/loading a shared library for 
in-process trace without checking for shared library support on the target.

* The signal.exp test case didn't test for signal support.

* The tspeed.c test case was failing to compile due to a missing 
#include, and its .exp file did not test for runtime target support in gdb.

Anyway....  here's an attempt to fix all this.  I added an early test 
for arch support to the .exp files so that most tests report 
"unsupported" immediately when they cannot possibly work, and fixed up 
the other problems as needed.

OK to check in?

-Sandra