transform CASE into if()..else if().. -> fixes 2 bugs (1)case within case statements, and (2)repeated elements in case options

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