RFR (XXS): 8208672: Enable -Wreorder in make files

[Thomas Schatzl]

Hi all,

  there have been several suggestions to try to fix the Hotspot code to
allow us to enable -Wreorder in the Hotspot sources.
This should make problems due to use-before-initialization much more
obvious.

This change enables -Wreorder for gcc and clang.

Of course it needs all previous RFRs sent to hotspot-dev to be checked
in first to result in successful compilation of the code.

Also checked by looking at the generated spec.gmk file which seems to
result in the flag in the I think "right" flag, but I am not very
knowledgable in this area.

build-dev is CC'ed.

CR:
https://bugs.openjdk.java.net/browse/JDK-8208672
Webrev:
http://cr.openjdk.java.net/~tschatzl/8208672/webrev/
Testing:
hs-tier1-4,jdk-tier1-3

Thanks,
  Thomas