Improved find_chars_in_sstring() a lot and documented how it works now.
Removed find_char_in_sstring() as it overlaps with find_chars...().
Improved documentation of SSTRING() so that it's less likely to be used incorrectly.
Removed additional ,
Fixed passing a wrong type to strchr().
Gave ret_value the correct type.
Changed the return type of 2 functions to long.

Mainly to increase accuracy and get it closer to size_t which is unsigned long.
Fixed an off by 1 error.