Halt if we get an error after folding
Spelling mistake
Continue as far as possible with errors on mismatching types

Also disabled op:error-then-continue for now, as code called later
(e.g. const fold) depends on these checks.
Added explicit conversion check for LL+fp -> fp
Floating point constant folding
Moved float const-fold test
Removed truncation checks for float->int constant casting
float -> int casts give an _int_ literal
Fixed signed long long -> long double constant-casting
Added long double test (for when ldbl support comes)