Added -DDBUG_ON to CXXFLAGS when compiling with debugging

This fixes a memory allocation bug in Innobase as structs was defined differently in .c and .cc files

configure.in

@@ -1681,12 +1681,12 @@ 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"