- document version requirements in the top-level file.
- remove incorrect version requirements from sub-dirs.
- set min. required version to 3.5 in top-level file.
- set minimun required version to 3.9 under docs/ .
- make documents building an option (on by default.)
so, the tree can be built using cmake-3.5 using
-DBUILD_DOCS=0 on the command line.
The 1.3.3 release didn't update the version number in the cmake
build. It's too late to fix the release, but bringing the version
number into sync allows the metaflac test which verifies the
encoder's embedded version number to pass, giving us proper test
feedback on other changes to the development tree.