Completely reworked implementation of generic constraints, by moving the generic constraint data from the symbols to the definitions (I originally thought that this would simplyfy things, but the more correct approach is to add it to the defs).

symsym.pas:
    - remove "tgenericconstraintdata" and any using/loading/writing of it in "ttypesym"
    - remove "tgenericconstraintflag"
symdef.pas:
    + add "tgenericconstraintdata"
    + load and write "genconstraintdata" in "tstoreddef"
symconst.pas:
    + add "tgenericconstraintflag" so it can be used in "ppudump" as well
defcmp.pas, compare_defs_ext:
    * as we allow global operator overloads we can't really determine whether two defs are compatible, because a valid operator for the specialization types might just happen to be in scope of the generic; so for now constraints are only strictly checked when declaring a specialization
pgenutil.pas:
    * adjust "parse_generic_parameters" and "check_generic_constraints" to the new location of the constraint data
ppudump.pp:
    * corrrectly parse defs which contain generic constraints

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24628 3ad0048d-3df7-0310-abae-a5850022a9f2