HEAD: inclusion order wrong for input.c

[Ralf Wildenhues]

Hello there,

CVS HEAD m4 currently gives me this warning on GNU/Linux:
| ../m4/m4/input.c:483: warning: implicit declaration of function 'strnlen'

which indicates that config.h wasn't included before string.h.  I'm a
bit at a loss to see right away how the structurually correct fix for
M4 would look like (include <config.h> from input.c, or from some other
header, ...), so no proposed patch.

Cheers,
Ralf