Don't allow libabc to load extensions at runtime.
Fix some #line annotations.
Fixing the previous bugfix.
Merge branch 'master' of github.com:CVC3/CVC4
Fix compiler warnings in arith and ITE utilities.
Add LETP (parallel let) to CVC4 native language.

Change CVC4 printer to use LETP by default.  CVC3 printer has no LETP.