Fixed a panic caused by over-optimizing npxdrop() in the non-FXSR case. frstor can trap despite it being a control instruction, since it bogusly checks for pending exceptions in the state that it is overwriting. This used to be a non-problem because frstor was always paired with a previous fnsave, and fnsave does an implicit fninit so any pending exceptions only remain live in the saved state.  Now frstor is sometimes paired with npxdrop() and we must do a little more than just forget that the npx was used in npxdrop() to avoid a trap later.  This is a non-problem in the FXSR case because fxrstor doesn't do the bogus check.
Fixed a panic caused by over-optimizing npxdrop() in the non-FXSR case.
frstor can trap despite it being a control instruction, since it bogusly
checks for pending exceptions in the state that it is overwriting.
This used to be a non-problem because frstor was always paired with a
previous fnsave, and fnsave does an implicit fninit so any pending
exceptions only remain live in the saved state.  Now frstor is sometimes
paired with npxdrop() and we must do a little more than just forget
that the npx was used in npxdrop() to avoid a trap later.  This is a
non-problem in the FXSR case because fxrstor doesn't do the bogus check.

FXSR is part of SSE, and npxdrop() is only in FreeBSD-5.x, so this bug
only affected old machines running FreeBSD-5.x.

PR:		68058

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase