* src/vm/jit/replace.h (executionstate_t): Added 'ra' field for return

* src/vm/jit/replace.h (executionstate_t): Added 'ra' field for return
address register. Otherwise replacement code for the PowerPC gets very
ugly, as the LR is not part of the intregs on PowerPC.

* src/vm/jit/replace.c (replace_executionstate_println): Added print
statements.
(replace_sanity_check_read_write): Check 'ra' field.

* src/vm/jit/alpha/linux/md-os.c (md_replace_executionstate_read):
Use new 'ra' field.
(md_replace_executionstate_write): Likewise.

* src/vm/jit/powerpc/linux/md-os.c (md_replace_executionstate_read):
Implemented for PowerPC/Linux.
(md_replace_executionstate_write): Likewise.