Remove the discard_const() macro

Declare dynamically allocated strings as 'char *' instead of 'const char *'.
Remove the discard_const() macro. Do not test whether or not a pointer is
NULL before calling free() because it is allowed to pass NULL to free().

Signed-off-by: Bart Van Assche <bvanassche@acm.org>

test-tool/iscsi-support.h

@@ -30,10 +30,6 @@
 #include "iscsi.h"
 #include "scsi-lowlevel.h"
 
-#ifndef discard_const
-#define discard_const(ptr) ((void *)((intptr_t)(ptr)))
-#endif
-
 extern const char *initiatorname1;
 extern const char *initiatorname2;