Generalize the native index fix to all instructions

It is possible to use natives in any instructions and their name should
evaluate to a native table index. But the patch in the previous commit
(bb4163ea456fab54385f7310b4e20949cda0aaa6) affected only SYSREQ.C
instructions, thus using natives with other instructions (for example,
with CONST.pri) would still result in an incorrect index.