Revert "toke.c: PL_in_eval purge"

Revert "toke.c: PL_in_eval purge"

This reverts commit 5c49e90fd624f3ab1cdb1f1d8e4f0525d7881b99.

This change broke line numbers under mad when the last statement in the main program lacks a semicolon.

I was mistaken in thinking that PL_rsfp would always be true when
PL_in_eval is false.

But the use of PL_in_eval is still wrong.  Under a mad build, we get
this inconsistency in line numbers:

$ perl -e 'print "\n-e undef\n"' > foo
$ ./miniperl foo
Use of uninitialized value in -e at foo line 2.
$ ./miniperl -we 'require "foo"'
Use of uninitialized value in -e at foo line 3.
foo did not return a true value at -e line 1.