Replace ctype.h functions with ascii ones

ctype.h is locale-dependent, so using it in our scanners is not optimal.
Let's be deterministic with our own simple functions.

Signed-off-by: Ran Benita <ran234@gmail.com>
rules: fix scanning of line-continuation without leading space

We were failing to scan something like\
this correctly.

Signed-off-by: Ran Benita <ran234@gmail.com>