Properly restore PL_curcop after /(?{})/

Properly restore PL_curcop after /(?{})/

C</$code/ or die> was reporting the place of dying as being in
an eval rather than in the main body of the code. This was because
when calling the code, we were setting PL_curcop to the inner code block
*before* doing the PUSH_MULTICALL, which happens to save PL_curcop;
the wrong value was then  being restored at the end of the function with
the POP_MULTICALL.

The fix is easy: just swap the two blocks of code that set PL_curcop and
do the PUSH_MULTICALL.