Always include errno.h

include/global.h:
  Portability fix
  (Using errno before including errno.h can give big problems on Linux)

include/global.h

@@ -223,6 +223,7 @@ double my_ulonglong2double(unsigned long long A);
 #define CONFIG_SMP
 #include <asm/atomic.h>
 #endif
+#include <errno.h>				/* Recommended by debian */
 
 /* Go around some bugs in different OS and compilers */
 #if defined(_HPUX_SOURCE) && defined(HAVE_SYS_STREAM_H)