Standardize SMT-LIBv2 set of logics to use LogicInfo.

Previously, SMT-LIB logics were treated specially, as in SMT-LIB v1.2.
This led to inconsistencies---such as nonstandard logics like "QF_LIRA"
being accepted in set-logic but not providing the "Real" sort.  Now,
the LogicInfo is used and queried, so nonstandard logics should work
fine and declare the correct symbols.  SMT-LIB v1.2, unfortunately,
can't take advantage of this fully since symbols like "Array" have
substantially different meanings in different logics.
Merge branch '1.2.x'
For SMT-LIBv2: to_real support; to_int and is_int support for constant expressions
more work on to_int/is_int