add iob_free and man page for iob_reset.

check in some windoze compat crap (still does not compile through for
windoze)

buffer/errmsg_warnsys.c

@@ -1,12 +1,10 @@
 #include <stdarg.h>
 #include <sys/types.h>
-#include <sys/uio.h>
 #include "errmsg.h"
 #include "str.h"
 #include <string.h>
 #include <errno.h>
 
-extern int errmsg_cvt(struct iovec* x,const char* message, va_list a);
 extern void errmsg_writesys(int fd,const char* message,va_list list);
 
 void errmsg_warnsys(const char* message, ...) {