Our only expectation of version number variables should be that
they begin with a decimal digit for VERSION_LESS, VERSION_EQUAL
and VERSION_GREATER comparison purposes. If people put extra
blah blah after a version number like "1.2.3 (this is some super
special extra information about our funky proprietary build of
the official 1.2.3 release)" then we should be ok with that.
So: now we have the following expectations for version number
variable content for the purposes of the AllFindModules test:
- it should start with a decimal digit (match "^[0-9]")
- it should not be empty
- it should not be VERSION_EQUAL 0
- it should not be NOT VERSION_GREATER 0
For all current build machines the modules FindPkgConfig, FindFreetype, and
FindLibXslt return a version number. Enforce this to early catch when this
is not always the case.