Added tracking of order by which tokens are processed by lexical analyser.
This helps in correctly formating error messages when constructs begin in one file, and end in another.

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