fix bug introduced a few commits ago: do not print the first char ('%') of a direct_variable_c (e.g. skip % in %IW4.2)

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