Fix bug: correctly generate code when accessing external variables declared inside FBs as a structured variable (realvar := fb1.fb2.extvar1.realvar)

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