Merging jdk7-b75 into Jigsaw

[Mark Reinhold]

> From: Mark Reinhold <mr at sun.com>
> Date: Fri, 06 Nov 2009 10:22:17 -0800

> ...
> 
> I'm starting to suspect something in my build environment.  I'll try a
> pure M5 build, without any Jigsaw changes, and see what happens.

Yep, same problem, but then I recalled the recent ALT_JDK_IMPORT_PATH
issue and noticed that my build script was still setting it.  Removing
that setting fixed the problem, though I'm not completely sure why.

It'd be nice to have a sanity check ensuring that ALT_JDK_IMPORT_PATH
is not set if SKIP_BOOT_CYCLE=false.

- Mark