drsym_lookup_address should not return Arm mapping symbols

Arm and AArch64 ABIs extend ELF with code mapping symbols to disambiguate code and data (and in the case of AArch32, they disambiguate Arm and Thumb). Symbols are generally $a, $t, $x and $d possibly extended with a suffix .xxxx.

What we are seeing is that diagnostics that call drsym_lookup_address() to find the function containing some address of interest, are (on Arm/Arm64) sometimes finding mapping symbols. This function should ignore mapping symbols. This would give consistent behavior across Arm and non-Arm architectures.

The mapping symbols might be useful for a query like "is this address Arm, Thumb, Arm64 or a literal pool?" but that's a different sort of query.

Basically, the mapping symbols aren't proper symbols, they are just there for technical reasons because that was a way to mark places in ELF - they could equally well have been relocations.

Seen on 9.0.