TEST: Tests for common/cosinetables.h and common/sinetables.h.

There is some duplication, but I thought it was a better idea
(lesser evil) to have them in separate classes.

At the moment we test for common angles and symmetry.
TEST: tests for common/huffman.h

A few tests for the Huffman decoder.

The encoding is the example from Wikipedia.
This could be improved by someone more knowledgeable by
generating one at runtime or using multiple encodings
which would each contain one edge case.
TEST: test cases for common/util.cpp
TEST: tests for common/rendermode.h

tests for parseRenderMode, renderMode2GUIO and getRenderModeCode.
TEST: reorganize test/common/util.h

Split a few test cases in two.
The resulting file is now better organized.
TEST: Thorough testing for common/hash-str.h

We test the various equal_to and hash functions therein.
TEST: Comments and cosmetical changes to some tests in test/common/.

cosinetables.h
hash-str.h
huffman.h
sinetables.h
util.h