trim whitespace

string trmwsp(string s) {
	if (strlen(s) < 1) {
		return empstr();
	}
	
	while (isspace(*s)) s++;
	
	if (*s == 0) {
		return empstr();
	}
	
	string end = s + strlen(s) - 1;
	while (end > s && isspace(*end)) end--;
	end++;
	
	string ts = malloc(sizeof(char *) * strlen(s));
	size_t len = strlen(s) - strlen(end);
	memcpy(ts, s, len);
	return ts;
}