Patch to prevent requiring memchr at compile time

[kothar]

See http://d.puremagic.com/issues/show_bug.cgi?id=10078 for full description.

If the std.string.indexOf(Char[], dchar, CaseSensitive) method is called at compile time with an ASCII dchar, it will fail:

/usr/share/dmd/src/phobos/std/string.d(345): 
    Error: memchr cannot be interpreted at compile time, 
    because it has no available source code

[WalterBright]

memchr is a heavily optimized function, and will be faster than doing it with a naïve loop. To make it work with ctfe yet keep the memchr, use:

if (__ctfe)
    ... loop ...
else
    ... memchr ...

[kothar]

Any better? I should have realised that, but of course was fixing it for myself rather than looking at the bigger picture!

[MartinNowak]

The control flow of this function is structured terribly, but if you don't want to rewrite the whole function you should return -1 here.

[MartinNowak]

superseded by #1417