Adding test files with manual examples to tst/testall.g

[olexandr-konovalov]

This may be an ignorant suggestion because I may be not aware of some features. Let me just tell you what I am doing in my packages (e.g. see wedderga package) and see if this may be interesting. Whenever the manual is built, examples are extracted (in makedocrel.g) and placed into the tst/chapterXX.tst files. These files are being tested with Test in tst/testall.g. If I add a new chapter with examples, I need only to add the call to Test to tst/testall.g