Fixed compile errors when compiling with HAVE_valgrind

sql/field.cc

@@ -7692,7 +7692,7 @@ my_decimal *Field_varstring::val_decimal(my_decimal *decimal_value)
 #ifdef HAVE_valgrind
 void Field_varstring::mark_unused_memory_as_defined()
 {
-  uint used_length= get_length();
+  uint used_length __attribute__((unused)) = get_length();
   MEM_MAKE_DEFINED(get_data() + used_length, field_length - used_length);
 }
 #endif

storage/innobase/include/srv0mon.h

@@ -656,7 +656,7 @@ Use MONITOR_DEC if appropriate mutex protection exists.
 
 #ifdef HAVE_valgrind
 # define MONITOR_CHECK_DEFINED(value) do {	\
-	mon_type_t m = value;			\
+    mon_type_t m __attribute__((unused))= value;        \
 	MEM_CHECK_DEFINED(&m, sizeof m);	\
 } while (0)
 #else /* HAVE_valgrind */

storage/innobase/page/page0cur.cc

@@ -1299,9 +1299,9 @@ page_cur_insert_rec_low(
 
 #ifdef HAVE_valgrind
 	{
-		const void*	rec_start
+		const void*	rec_start __attribute__((unused))
 			= rec - rec_offs_extra_size(offsets);
-		ulint		extra_size
+		ulint		extra_size __attribute__((unused))
 			= rec_offs_extra_size(offsets)
 			- (rec_offs_comp(offsets)
 			   ? REC_N_NEW_EXTRA_BYTES
@@ -1530,9 +1530,9 @@ page_cur_insert_rec_zip(
 
 #ifdef HAVE_valgrind
 	{
-		const void*	rec_start
+		const void*	rec_start __attribute__((unused))
 			= rec - rec_offs_extra_size(offsets);
-		ulint		extra_size
+		ulint		extra_size __attribute__((unused))
 			= rec_offs_extra_size(offsets)
 			- (rec_offs_comp(offsets)
 			   ? REC_N_NEW_EXTRA_BYTES