[PATCH] Replace drivers/net/wan custom ctype macros with standard ones

Replace the custom is_digit()/is_hex_digit() macros with
isdigit()/isxdigit() from <linux/ctype.h> Additionaly remove unused macro
is_alpha() from <linux/wanpipe.h>

Signed-off-by: Tobias Klauser <tklauser@nuerscht.ch>
Cc: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>