base: Fix multiple names to one address bug in SymbolTable

base: Fix multiple names to one address bug in SymbolTable

The SymbolTable class currently assumes that at most one symbol can
point to a given address. If multiple symbols point to the same
address, only the first one gets added to the internal symbol table
since there is already a match in the address table.

This changeset converts the address table from a map into a multimap
to be able to handle cases where an address maps to multiple
symbols. Additionally, the insert method is changed to not fail if
there is a match in the address table.

Change-Id: I6b4f1d5560c21e49a4af33220efb2a8302961768
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andreas Hansson <andreas.hansson@arm.com>
Reviewed-by: Gabor Dozsa <gabor.dozsa@arm.com>