RFR(S): 8077618: Move rtmLocking.cpp to shared directory.

[Lindenmaier, Goetz]

Hi,

we implemented support for Transactional Memory on ppc.  For this, we need
the file rtmLocking.cpp from subdirectory x86 as is.

Therefore I would like to move the file to share/vm/runtime, where the
corresponding header is placed.  I added a guard around the code in this file.

Also, I moved #ifdef x86 from globalDefinitions.hpp to globalDefinitions_x86.hpp
which simplifies enabling RTM on PPC.

Please review this change.  I please need a sponsor.
http://cr.openjdk.java.net/~goetz/webrevs/8077618-mvRTM/webrev.01/

Best regards,
  Goetz.