0023372: "diffimage" using in tests commands

0023372: "diffimage" using in tests commands

Comparison of images is implemented in testdiff command; output in HTML form generated
Add measurement of memory (working set) delta in test case execution
Add memory statistics to output of testdiff command
Treatment of parameter -outdir of command testgrid corrected.
Function locate_data_file and code to run tests in parallel revised to be usable with Tcl 8.4.
Added function testsummarize: regenerate summary log of tests from test case logs
Command testdiff is protected against exception raised by diffimage if images have different formats