Second self-hosting fixpoint: stage-3 (hand source compiled by stage-2,
itself compiled by stage-1) produces byte-identical IR to stage-2 at
59974 lines. New since v0.1.0: string subscript, char literals, const
open arrays, array literals, static arrays, Low/High, PChar, @expr
address-of, set types, GetEnvironmentVariable, and the four SysUtils
path functions. Also fixes _CurrentExceptionMessage (was always empty
due to _PopExcFrame being called before the except body).
87597605cc