Fix systemtap.examples/process/syscalltimes script and add test.

Fix systemtap.examples/process/syscalltimes script and add test.

stap was a little too smart for the script, optimizing out unused
variables and producing WARNINGS/ERRORS for deleted variables.
Make all variable manipulation conditional on their actual usage,
add -w to surpress warnings, add a new option -c 'process' to run
during script invocation and add a meta testcase for the testsuite.