[GCC-XML]__int64 support for mscv6

[Brad King]

> Wouldn't it make more sense to have the read/parse functions look for
> long long and use that *instead of* __int64?  I.e., to pretend that VC
> implements __int64 as a macro for long long?  After all, long long is
> part of C99 (granted, not specifically for 64-bit integers...)
>
> Or is the read/parse code generating other code that will be consumed by
> vc6 (in which case long long would be *very bad*).

Yes, this is the case for some projects using GCC-XML.  They should be
able to know whether the __int64 was written in the source or not.  Now
that long long is part of C99, future MSVC versions will probably support
both.  Then GCC-XML will have to further modify the GCC parser to add an
actual fundamental type called __int64 instead of using the macro trick.

-Brad