[tlbuild] asymptote build

[Akira Kakuto]

Hi Angelo,

> Anyway they are *all* Cygwin-1.5 binaries! and doesn't look a good 
> strategy mixing win32 and Cygwin binaries. But this is only my opinion...

Native win32 port of asymptote is very difficult for me,
because I have to emulate fork, and so on ...
Therefore I asked Karl to use the original Cygwin-built one.
Eventually I expect that Karl and others will move asy.exe, cygwin1.dll,
freegult.dll and glu32.dll in a hidden directory, and write a
wrapper "asy.bat" in the bin/win32 directory which calls the
binaries in the hidden directory.

Thanks,
Akira