Agena2.20.3

Bug Fixes:

• `reduce` inadvertently deleted a user-defined global variable _c. This has been fixed.
• In ill-fated situations, factories written in C may have caused problems with the internal table that stores all constants, potentially causing segmentation faults. This has been fixed.

Changes to the C API:

• Removed unused or obsolete C API functions agn_stackborders, agn_isvalidindex, agn_absindex, agn_calloc, agn_free, agn_rawgetifield, lua_seqrawget2, agn_regrawget2, agn_getseqlstring.
• Renamed C API function agn_datetosecs to agnL_datetosecs, and agn_pairgetinumbers to agnL_pairgetinumbers, agn_paircheckbooloption to agnL_paircheckbooloption.
• `lua_seqrawget` now needs a third argument which controls whether in case of a non-existent key `null` or an error will be issued.
• `agnL_geti` can now process pairs and strings.
• Removed various C API macros.