RFR 8074717: Merge interp_masm files for x86 _32 and _64

[Coleen Phillimore]

Summary: Merge duplicate code and use #ifdef for non-mergeable sections.

Inspired by Max's change and because I was working on this with him, 
I've merged interp_masm_x86_32 and _64.cpp/hpp files.

There are two webrevs generated.  The first webrev is generated to see 
the diffs.   Mostly the _64 contents are chosen because the formatting 
was better.  The second is moving the code into the already existant 
interp_masm_x86.cpp/hpp files.

Ran all jck tests on this and JPRT, also ran NSK vm.quick.testlist which 
includes jvmti tests.

bug link https://bugs.openjdk.java.net/browse/JDK-8074717
open webrev at http://cr.openjdk.java.net/~coleenp/8074717
open webrev at http://cr.openjdk.java.net/~coleenp/8074717_2/

Thanks,
Coleen