The regex to detect the beginning of a test file execution was too
broad, matching any line beginning with "Running ". This caused
dg-extract-results.sh to truncate some test logs, including
gdb.base/help.exp (which tests "help running", printing "Running the
program.")

The attached patch makes the match a little more precise to avoid
this. With this the exact count of PASS/FAIL/etc lines in the
dg-extract-results.sh output matches the counts in the computed
summary exactly for all cases I've seen.