#3497 printf function family crashes sdcc when compiled in c2x mode

[Philipp Klaus Krause]

The following standard library functions crash sdcc when compiled in c2x mode:

printf_large.c
printfl.c
sprintf.c
vprintf.c
ds390/lcd390.c

For now, I will put a #pragma std_c11 as a workaround.

[Philipp Klaus Krause]

Fixed in [r13841].