- Improve Makefile.am for both prebuilt tables files
- On the way, tidy EXTRA_DIST: Move the header files to noinst_HEADERS,
where they conceptually belong, and add missing SECURITY.md to EXTRA_DIST
This header contains a static array that replaces the ecmult_context pre_g and pre_g_128 tables.
The gen_ecmult_static_pre_g program generates this header file.