Added new STRNCMP_EQUAL(expected, actual, length) macro used to compare up to 'length' characters from 'expected' and 'actual' strings.
In UtestShell::assertCstrNEqual : Replaced type of parameter 'int length' with 'size_t length'
Added tests for STRNCMP_EQUAL macro.
Added checks for macro STRNCMP_EQUAL failuers. Removed unnecesary macro tests in SimpleString test group
Merge pull request #347 from PrzemekWirkus/strncmp_equal

STRNCMP_EQUAL - C string comparison of the first n characters