(XS) RFR: 7008747: Header files with conditional behaviour can not be precompiled

[David Holmes]

Bug: https://bugs.openjdk.java.net/browse/JDK-7008747

webrev: http://cr.openjdk.java.net/~dholmes/7008747/webrev/

A trivial clean up to ensure no confusion. The bug might be better 
described in the reverse sense: files that modify the behaviour of 
included headers must not use precompiled headers.

In this case the code looks like it is using PCH when in fact it will be 
disabled on this platform. Better to be 100% clear (like the PPC code 
involving the same definitions) and not include precompiled.hpp

If any zero folk see this then zero may also want a cleanup here as it 
defines DONT_USE_REGISTER_DEFINES, but doesn't seem to include and 
headers that are conditionalized on that value.

Thanks,
David