<strings.h> as the associated header file.
The prototypes have been moved there from <string.h> because
POSIX.1-2001 said so.
- Conditionally include either <strings.h> or <string.h> based
on whether the [r]index() or str[r]chr() functions are
compiled, respectively.
- Style(9) tells us to
- put a space after the return keyword
- to check for a NUL character without using the ! operator.
- use NULL instead of (type *)NULL where the compiler knows
the type.
Apply these rules.
- Rather use ANSI-C function definitions than K&R ones.
- For index(3), correct second function argument's type; it was
declared to be a `const char' before and is now an `int'.
