configure.in:

  Add -DDBUG_ON to CXXFLAGS whenever it is added to CFLAGS.
  Thus, sql/ha_innodb.cc will be compiled with the same
  setting of UNIV_DEBUG as the rest of InnoDB,
  i.e., --with-debug enables InnoDB ut_ad() assertions
  everywhere.

configure.in

@@ -1632,12 +1632,12 @@ if test "$with_debug" = "yes"
 then
   # Medium debug.
   CFLAGS="$DEBUG_CFLAGS $DEBUG_OPTIMIZE_CC -DDBUG_ON -DSAFE_MUTEX $CFLAGS"
-  CXXFLAGS="$DEBUG_CXXFLAGS $DEBUG_OPTIMIZE_CXX -DSAFE_MUTEX $CXXFLAGS"
+  CXXFLAGS="$DEBUG_CXXFLAGS $DEBUG_OPTIMIZE_CXX -DDBUG_ON -DSAFE_MUTEX $CXXFLAGS"
 elif test "$with_debug" = "full"
 then
   # Full debug. Very slow in some cases
   CFLAGS="$DEBUG_CFLAGS -DDBUG_ON -DSAFE_MUTEX -DSAFEMALLOC $CFLAGS"
-  CXXFLAGS="$DEBUG_CXXFLAGS -DSAFE_MUTEX -DSAFEMALLOC $CXXFLAGS"
+  CXXFLAGS="$DEBUG_CXXFLAGS -DDBUG_ON -DSAFE_MUTEX -DSAFEMALLOC $CXXFLAGS"
 else
   # Optimized version. No debug
   CFLAGS="$OPTIMIZE_CFLAGS -DDBUG_OFF $CFLAGS"