[fpc-pascal] A warning when Blockwriting/reading dynamic array pointers

[DaWorm]

IMO, a dynamic array should never be part of a structure that is
passed to BlockWrite in the first place.  Not that I use many dynamic
arrays in the first place, but to me they pass over the border between
simple data types (that are fine for BlockWrite) and managed data
types (that have quite a lot of "gotchas").  I lump them in with
TObjects in that respect.