The "smart" PLP handler tries to recover the flags from an earlier
PHP. The non-smart version just marks all the flags as indeterminate.
This doesn't work well on the 65816 in native mode, because having
the M/X flags in an indeterminate state is rarely what you want.
Code rarely uses PLP to reset the flags to a specific state, preferring
explicit SEP/REP. The analyzer is more likely to get the correct
answer by simply leaving the flags in their prior state.
A test case has been added to 20052-branches-and-banks, which now has
"smart PLP" disabled.
