small header change to correct an unnecessary compiler warning

[Agthorr]

I'm running GNU libc version 2.2.3.

I recently noticed that the function strtol() is declared as follows:

extern long int strtol (__const char *__restrict __nptr,
                        char **__restrict __endptr, int __base) __THROW;

This causes a warning to be generated unnecessarily for the following
perfectly legimate code:

------------------------------------------------------------------------
#include <stdlib.h>

int main(void) {
        char bloop[] = "123";
        const char *foo = bloop;

        strtol (foo, &foo, 0);

        return 0;
}          
------------------------------------------------------------------------

The warning is:
test.c: In function `main':
test.c:7: warning: passing arg 2 of `strtol' from incompatible pointer type

If you changed the declaration of __endptr as show below, it would
eliminate this warning, without breaking any existing code:
        __const char **__restrict __endptr

This can be guaranteed not to break anything, since casts from
"char **" to "const char **" are implicit.  Also, this won't break
strtol(), since it modifies *__endptr, but never **__endptr.

In fact, although "const" is usually associated with being more
restrictive, this would allow a superset of code to compile without
warnings.

strtoul(), strtod(), and similar functions suffer from the same problem.

It's a small complaint, but it's also easy to correct!

-- Agthorr