ref: 261ec9fe0e0b2dbde909da79a93e90220a9ea62c
dir: /sys/src/libc/port/runestrncat.c/
#include <u.h>
#include <libc.h>
Rune*
runestrncat(Rune *s1, Rune *s2, long n)
{
	Rune *os1;
	os1 = s1;
	s1 = runestrchr(s1, 0);
	while(*s1++ = *s2++)
		if(--n < 0) {
			s1[-1] = 0;
			break;
		}
	return os1;
}