Major code cleanup: IL code generation now uses symbol.datatype (filled in during stage3 data type checking) instead of determining the symbol's datatype by itself.

STD_TEST.st
STD_RESSOURCE.c
LOCATED_VARIABLES.h
POUS.c
test
STD_CONF.c
SFC_TEST.st
test.exe
plc.st
POUS.h
VARIABLES.csv