Revert "remove file.c"

This reverts commit 4cf8f3d7f6b822c29be481f0d1f6f0a856bd847b.
Revert "remove eval.c and load.c"

This reverts commit 6a1b7c372d9fb0f06d983cd5ffff6307c9e2c6ab.
refactor load
Revert "remove time.c and system.c"

This reverts commit bd2c5afb02282a19594dad811e887c2de3fd98c4.