mbt 2.1.1

Fixes two false positives of 2.1.0's module-data check (#150):

• Files are scanned as cc370 compiles them for MVS: make runs each through cc370 -E with the project's CFLAGS, so host-only branches (#ifndef __MVS__) no longer count.
• static const struct { … } tbl[] = … is read as const.

On a large interpreter project: 25 warnings → the one real case. Each file is preprocessed once and in parallel (~1–3 s on the largest projects).

Bump to this release, not to 2.1.0.