Add a TCL interface to this new capability and add tests cases to the TCL
test scripts to actually use the new capability.
FossilOrigin-Name: ad8bc68197f2b47435149c3dbc035f4e7210fc76
Do not allow constant initialization to occur once control flow has a chance
to diverge, to avoid the possibility of having uninitialized registers.
Ticket [80ba201079ea60807].
FossilOrigin-Name: c5c53152d68218bb5e7f922271dd7c50da2361c1