RTL math.pas on the crtl dd kernels — correct rounding for Pascal too

• Track: B (lib/rtl/math.pas + lib/crtl/src/math.c). Tag: compat. Rainy-day (user 2026-07-19: "not bothered for now").

crtl's libm is correctly rounded across the whole surface (b377-b385 dd kernels); Pascal's Exp/Ln/Sin/... are the old ~1-ulp series. Route the Pascal routines onto the C kernels (Pascal wraps C — the REVERSE of the old direction), so Pascal inherits correct rounding free and there is one libm.

Notes for the implementer:

• Pascal Exp calling __crtl_exp is binding-safe (no case-insensitive collision — that hazard is only same-name, see the b377 landmine).
• Self-host implications: if the compiler binary itself uses Exp/Ln (float printing, constant folding), its output bits change -> reseed / codegen- differ expected on the transition commit ([[codegen-reseed]] memory).
• Single/overload surface of math.pas must keep its FPC-compat signatures.
• The dd kernels live in C sources; a Pascal program today only links crtl when C objects are present — needs a pull path (builtin unit or crtl-as- unit) before Pascal can call them. That plumbing is the actual work.

Moved to rainy-day/ (2026-07-20, Track B sweep)

The ticket already records the user's 2026-07-19 call: "not bothered for now". It was still in backlog and still ranked. Moved to match the decision that was already made.