Streamlined the handling of 'exectimeout' in sub_test.
Eliminated 'comptimeout' variable from sub_test
following Kyle's reviewer feedback.
Merge pull request #766 from vasslitvinov/fix2-exectimeout-in-sub_test

Streamlined the handling of 'exectimeout' in sub_test.

sub_test used 'exectimeout' - which indicates test execution timeout -
where it meant compilation timeout, besided its intended use.

I replaced these inappropriate uses with 'False', because that's
always the value it would have at those points.

Also I eliminated the initialization of 'exectimeout'
that's no longer needed:

-----------
for testname in testsrc:
    exectimeout = False  <-------------------------- not needed
    for compopts in compoptslist:
        for texecopts in execoptslist:
            for count in xrange(numTrials):
                exectimeout = False
                ... if there is a timeout:
                        exectimeout = True
                if not exectimeout:
                    ... run prediffs ...
                    ... report test success or failure ... 
                if perftest:
                    if exectimeout or status != 0:
                        break
-----------

An earlier commit 626504a also introduced the variable 'comptimeout'.
Kyle suggested it was not needed, so I took it out.

Reviewed by Kyle.