hghave: update cvs112 description

Classic cvs stopped at 1.11.
There was a beta version 1.12 that never had a final release.
CVS NT is a fork which starts with versions numbered 2.0+.

We should have an hg have cvsnt, but to test that requires getting
cvsnt, and it's commercial / its older source versions are
hard to find.

tests/hghave.py

@@ -111,7 +111,7 b' def has_cvs():'
     re = r'Concurrent Versions System.*?server'
     return matchoutput('cvs --version 2>&1', re) and not has_msys()
 
-@check("cvs112", "cvs client/server >= 1.12")
+@check("cvs112", "cvs client/server 1.12.* (not cvsnt)")
 def has_cvs112():
     re = r'Concurrent Versions System \(CVS\) 1.12.*?server'
     return matchoutput('cvs --version 2>&1', re) and not has_msys()