Remove the sysutils Move/FillChar copies (now shadowed by builtin)

• Type: task (library cleanup) — Track B (lib/** ownership)
• Status: DONE 2026-07-04 — removed both decls (interface) + both bodies (impl) from lib/rtl/sysutils.pas; builtin Move/FillChar (in pin v171, well past v145) resolves every call. make lib-test green (sysutils test incl.)
  • 19 demos OK against pinned v171. No behavior change (byte-identical impl).
• Opened: 2026-07-02 by Track A while landing the builtin-home half of [[feature-move-fillchar-intrinsics]] (v145).

Move/FillChar moved to compiler/builtin/builtin.pas (auto-pulled, no uses needed, FPC System parity). The identical copies in lib/rtl/sysutils.pas (interface ~line 95, impl ~line 347) are now dead weight: builtin registers first, so FindProc resolves every call to the builtin versions. Track A did not touch lib/** per file-ownership rules.

Remove the two decls + two bodies from sysutils; make lib-test + demos green against a pin that includes v145 (the builtin versions must be in the stable binary BEFORE the copies disappear, else sysutils users lose the symbol). No behavior change expected — the implementations are byte-for-byte the same Pascal.