mozilla's install hanging on amd64

[Mikhail Teterin]

> patches for -march-related bugs welcome" (most reasonable IMNSHO)

*All* patches are welcome -- including -march-related ones. That -march should 
work follows simply from the documented CPUTYPE setting and the bsd.cpu.mk 
"magic". Porters' handbook can help in _clarifying_ this, true.

When mozilla compiles on amd64, plenty of warnings are thrown up regarding 
conversions between pointers and integers of different size. Could this be my 
problem -- exposed by some opteron-specific trick in gcc?

	-mi