cpp: test: Reduce number of non-extended tiff tests

Reduce the combinations by a factor of ten.
cpp: test: Header tests are extended tests

Only build when extended tests are enabled.
cmake: Add API stability warning
docs: Document C++ API stability guarantee for 5.2
Correct version embedding
Update Travis to build the 'utils' Ant target
Update version history for 5.0.6
Remove documentation note from 5.0.6 list
Merge pull request #1416 from melissalinkert/rebased/develop/5.0.6-history

Update version history for 5.0.6 (rebased onto develop)
Merge pull request #1413 from rleigh-dundee/cpp-version

C++: Correct version embedding
Merge pull request #1395 from rleigh-dundee/cpp-fixes

C++: Various minor fixes
Merge pull request #1415 from melissalinkert/travis-utils

Update Travis to build the 'utils' Ant target