#479 part 1 (int literal suffixes)
Closes #749. Suffix-less fp literals are Double

Issue #749 is about supporting suffixes in int and float literals. To
align with C/C++, float literals are now of type 'Double' by default,
and you need the suffix 'f' to turn them into 'Float's. The 'l' suffix
turns them into 'LDouble's.