debuggerd: Show function names in tombstone backtraces

This change enables debuggerd to provide backtraces with function
names in tombstone files and log messages.  It does this by reading
the image file that the address is found in, and parsing the dynamic
symbol table to try to extract the symbol corresponding to the given
address.

This works best when "-Wl,-export-dynamic" is added to the LDFLAGS
of each library and executable, because this will cause all symbols
to be added to the dynamic symbol table.  If this flag is not present,
it will still work, but it will only be able to identify functions
which are part of the external API of the library/executable.

Change-Id: I618baaff9ed9143b7d1a1f302224e9f21d2b0626