DynaLoader 1.36 dl_find_symbol add 3rd optional argument

DynaLoader 1.36 dl_find_symbol add 3rd optional argument

On Darwin DynaLoader::bootstrap tries dl_find_symbol first with libhandle 0,
to see if the shlib with the symbol is already loaded, e.g. with libc.
We do not want to store the dl_last_error information for this mostly
failing probe, so add an optional ign_err=0 argument.
Similar for dl_find_symbol_anywhere, which is expected to fail for all librefs.

Also support dl_last_error on symbian, as on all other platforms.

TonyC: fix bad XS