The VHDL sources of JanusHDL's built-in libraries, exactly as the programs
use them: a reference to read. Messages cite these paths (for example
ieee/numeric_std-body.vhdl). Editing them changes nothing; the programs
carry their own copies.

std/, ieee/  The IEEE 1076-2019 packages, unmodified (Apache-2.0:
             LICENSE-ieee.txt, AUTHORS-ieee.md), and JanusHDL's synthesis
             contexts (ieee/ieee_std_context.vhdl, ieee_bit_context.vhdl).
ieee93/      std_logic_1164, numeric_std and numeric_bit for VHDL-93 and
             VHDL-2002 designs, generated from IEEE's 2019 sources
             (Apache-2.0).
legacy/      The legacy arithmetic packages (std_logic_arith,
             std_logic_unsigned, std_logic_signed, std_logic_misc) and the
             VHDL-93 std_logic_textio, under the notice in legacy/NOTICE.txt;
             std_logic_textio with one fix, marked in the file.
