Traditionally, our maps were mostly implemented via macros that had
weird call semantics. This shows in our index code, where we have macros
that insert into an index map case-sensitively or insensitively, as they
still return error codes via an error parameter. This is unwieldy and,
most importantly, not necessary anymore, due to the introduction of our
high-level map API and removal of macros.

Replace them with inlined functions to make code easier to read.