Added support for type helpers. In non Delphi modes they use "type helper" and in mode Delphi they use "record helper". They can also be used on constants.

symconst.pas:
  + extend "thelpertype" by "ht_type" which tells the code in "pdecobj.parse_extended_type" that a type helper declaration has been parsed
node.pas:
  + add a constant which identifies all constant node types
ptype.pas:
  + read_named_type: add a parameter "hadtypetoken" to tell the code whether a "type" token had been parsed before
  + read_named_type: if an identifier "helper" is parsed we need to check whether "hadtypetoken" is true and the modeswitch "m_class" is set, but the "m_delphi" one is not; in that case we have a "type helper" declaration
pgenutil.pas, generate_specialization:
  * adjust call to read_named_type
pdecl.pas, types_dec:
  * adjust call to read_named_type

pdecobj.pas:
  * parse_extended_type: extend for correct handling of primitive types (includes Delphi compatible handling as well) and reject types that are explicitly not allowed
  * method_dec: require "static" for class methods in type helpers
  * method_doc: allow constructors for type helpers as well
paramgr.pas, tparamanager:
  * set_common_funcretloc_info: handle type helper constructors like record constructors
  * handle_common_ret_in_param: the "self" value of a type helper constructor is also returned in a parameter
pexpr.pas:
  + add a function to postfixoperators which tries to find and apply a type helper for a given type
  * postfixoperators: try to apply type helpers for ordinal constants
  * postfixoperators: use the correct string type for string constants
  * postfixoperators: try to apply type helpers for enum constants
  * postfixoperators: try to apply type helpers for arrays
  * postfixoperators: try to apply type helpers for Variant
  * postfixoperators: try to apply type helpers for pointer types
  * postfixoperators: try to apply type helpers for other types
  * factor: check postfixoperators after _REALNUMBER, _CCHAR, _CWCHAR, _TRUE and _FALSE
  * factor: also check postfixoperators if a _POINT follows a _NIL

symdef.pas, tdefawaresymtablestack.addhelpers:
  * use "generate_objectpascal_helper_key" to generate the key
symtable.pas:
  + add function to generate the key value for the map of extended types using the extended def
  * adjust "search_last_objectpascal_helper" and "search_objectpascal_helper" to handle primitive types as well
  * use the new "generate_objectpascal_helper_key" function to generate the key

pparautl.pas:
  * insert_self_and_vmt_para: don't insert the $vmt symbol for record or type helpers (ToDo: check whether class helpers really need the symbol as well)
  * insert_self_and_vmt_para: pass "self" as var parameter for type helpers as well
psub.pas, generate_bodyentry_block: 
  * also allow type helpers for constructor methods
ncal.pas, tcallnode.gen_self_tree:
  * also use a temp variable for type helper constructors
ncgcal.pas, tcgcallnode.secondcallparan:
  * allow Pointers to be passed as address param if it is the Self value of a type helper extending a pointer type
  * correctly handle the location in case of type helper constructors

+ add tests

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@23580 3ad0048d-3df7-0310-abae-a5850022a9f2