error() function is glibc-specific, make own implementation

plagmax.c

@@ -1,7 +1,6 @@
 #include <stdio.h>
 #include <sys/mman.h>
 #include <string.h>
-#include <error.h>
 #include <errno.h>
 
 #include "config.h"
@@ -173,7 +172,9 @@ double nodes2mb(pos_t n) {
 	return sizeof(struct node) * (double)n / (double)(1 << 20);
 }
 
-int main(void) {
+int main(int argc, const char *argv[]) {
+	init_err();
+
 	bit_t b[IPMAXLEN];
 	mask_t m;
 	char s[BUFLEN];