no need to GC scan the .rodata segment

- Also _deh_end will have to live in .data for PIC code
  (Bugzilla 11171), so it can't be used as end of .rodata.
Merge pull request #715 from MartinNowak/dontScanRODATAonFBSD

[dll] FreeBSD must not GC scan .rodata
Replace AssociativeArray struct with UFCS methods