Unsupported size error for clean call argument sp_action in stack_x86.c, when run under debug mode.

Hi.

Setup:
x86-64 linux.
Running leaks_indrect.c from the tests.

Failing run command:
bin64/drmemory -debug -dr_debug -- leak_indirect

Running x86 master branch with fastpath off and shared_slowpath off causes an error:

`

rsi instruction.

When I had this problem when developing the aarch64 port, doing the OPND_CREATE_INT32(sp_action) wrap fixed it as aarch64 doesn't hit the same 'no encoding found' assert after.

This problem does away entirely when you omit:
'-debug -dr_debug'

Let me know if you need anymore info.

Greg.