add iob_free and man page for iob_reset.

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

buffer/errmsg_writesys.c

@@ -1,6 +1,16 @@
 #include <stdarg.h>
 #include <sys/types.h>
+#ifdef __MINGW32__
+#include "windows.h"
+#include <unistd.h>
+
+struct iovec {
+  LPCVOID iov_base;
+  DWORD iov_len;
+};
+#else
 #include <sys/uio.h>
+#endif
 #include "errmsg.h"
 #include "str.h"
 #include <string.h>
@@ -22,5 +32,13 @@ void errmsg_writesys(int fd,const char* message,va_list list) {
   x[i+1].iov_base="\n";
   x[i+1].iov_len=1;
 
+#ifdef __MINGW32__
+  {
+    int j;
+    for (j=0; j<i+2; ++j)
+      write(2,x[j].iov_base,x[j].iov_len);
+  }
+#else
   writev(2,x,i+2);
+#endif
 }