Makes some white-space differences in most output, plus a few cases
where more could have been put out but was cut short by the previous
fix-sized buffer.
Implement token pasting as per the C++ specification, within the current
style of the PP code.
Non-identifiers (turning 12 ## 10 into the numeral 1210) is not yet covered;
they should be a simple incremental change built on this one.
Addresses issue #255.
If this breaks your AST consumer, best is to modify it to test
against the enum values instead of doing string comparisons on
built-in function names. This is the reason the change was made.
If you need the old behavior, you should be able to get it back by changing
PureOperatorBuiltins to be false instead of true. This path will work for
a while, but is marked deprecated.
Also, the old behavior is tagged as release 2.4.
