RFR (S,trivial) 8200276: Cleanup allocation.hpp includes

[coleen.phillimore at oracle.com]

These includes are no longer needed with VALUE_OBJ_CLASS_SPEC removed in 
these files.

open webrev at http://cr.openjdk.java.net/~coleenp/8200276.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8200276

Tested tier1 on oracle platforms: linux-x64, solaris-sparc, macos-x86, 
windows-x86.  Tested open-only with --disable-precompiled-headers.  
Built zero on linux x64.

Thanks,
Coleen