Start of std2

[Bill Baxter]

A modest start, but here's a quickie port of D2.x std.conv,std.traits, 
and std.variant to D1.x.

Not really tested at all, but they pass unit tests!
So if they're broken then blame it on the guy who wrote the unit tests.  :-)

http://www.billbaxter.com/tmp/std2.zip

[Actually conv doesn't pass it's unittests for D2.0 either.  Conversion 
of "nan" to floats doesn't work. On Windows at least -- maybe Linux's 
strtof is smarter.]

--bb