implement Nikola's idea to remove limit number of strings in errmsg

buffer/errmsg_write.c

@@ -0,0 +1,20 @@
+#include <stdarg.h>
+#include "errmsg.h"
+#include "errmsg_int.h"
+
+void errmsg_write(int fd,const char* err,const char* message,va_list list) {
+  errmsg_start(fd);
+  errmsg_puts(fd,message);
+  for (;;) {
+    const char* s=va_arg(list,const char*);
+    if (!s) break;
+    errmsg_puts(fd,s);
+  }
+  va_end(list);
+  if (err) {
+    errmsg_puts(fd,": ");
+    errmsg_puts(fd,err);
+  }
+  errmsg_puts(fd,"\n");
+  errmsg_flush(fd);
+}