[8u] 8078437: Enable use of devkits for Windows.

[Kevin Walls]

Hi,

I'd like to get a review of a backport from 9 to 8u:

8078437: Enable use of devkits for Windows.
JBS: https://bugs.openjdk.java.net/browse/JDK-8078437

9 changeset:
URL:   http://hg.openjdk.java.net/jdk9/dev/rev/bc02cff96b92

9 review thread:
http://mail.openjdk.java.net/pipermail/build-dev/2015-April/014870.html

8u webrev: http://cr.openjdk.java.net/~kevinw/8078437/webrev.00/

common/autoconf/toolchain_windows.m4  ...this one had some manual work, 
but some of that was just re-indenting.
common/autoconf/toolchain.m4 change didn't import but the line split in 
the if statement looks cosmetic anyway.  I copied it as I'm here.
Other files import OK, plus regenerating the generated files.

With this change, the regular build still works as before, plus we can do:

$ bash ./configure --with-toolchain-version=2013 --with-devkit=/devkitdir
..and e.g. make images uses that compiler.

(that does also need the hotspot change 8203349, but 2013 is the devkit 
bundle I have to hand)

Thanks!
Kevin