Add pointer type infrastructure: ^T types, dereference, GetMem/FreeMem/ReallocMem
- uSymbolTable: tyPointer kind, TPointerTypeDesc(BaseType), GetMem/FreeMem/ReallocMem builtins
- uLexer/uPasTokeniser: tkCaret token for '^'; suppress ^X string escape (not in Clean Pascal)
- uParser: ParseTypeName handles '^TypeName' prefix (uses Self. for explicit recursion);
TDerefExpr for P^ postfix; TPointerWriteStmt for P^ := V lhs
- uAST: TDerefExpr, TPointerWriteStmt nodes
- uSemantic: FindTypeOrInstantiate creates TPointerTypeDesc on demand for '^T';
AnalyseDerefExpr, AnalysePointerWriteStmt; GetMem/ReallocMem/type-cast handling
- uCodeGenQBE: tyPointer→'l', EmitPointerWrite (storew/storel), TDerefExpr (loadw/loadl),
GetMem→malloc, FreeMem→free, ReallocMem→realloc, pointer arithmetic (extsw + add/sub),
type-cast via copy
- 15 new tests (556 total), all passing
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