class keyword needed before friend
Add warning for GCC under version 4.7.

- lower versions are not supported
Some corrections (mainly typos) in reference manual.
Minor improvements in build and test system.

- ignore *.orig
- *.tst rules in tests directories; to run only one con file
- commented recepie to coberture usage (cover testst)

Conflicts:
	.gitignore
	unit_tests/system/tokenizer_test.cpp