Faster IcedTea builds

[Gary Benson]

Francis Kung wrote:
> I've just committed a change into the IcedTea repository providing a
> fast-build option: if you pass --enable-fast-build to configure, it
> will build with -O0 (instead of -O3) and will skip building all the
> javadoc.
> 
> This speeds up the build by about 30-50% for me, which may be useful
> to those doing development work.

Good call.  I switched to -O0 locally, but I didn't think to make it
available like that.

Cheers,
Gary