Do not use Valgrind client requests in a normal release build, they have a...

Do not use Valgrind client requests in a normal release build, they have a small but noticable performance impact.

include/my_valgrind.h

@@ -23,7 +23,7 @@
 #define IF_VALGRIND(A,B) B
 #endif
 
-#if defined(HAVE_VALGRIND)
+#if defined(HAVE_VALGRIND) && defined(HAVE_valgrind)
 # include <valgrind/memcheck.h>
 # define MEM_UNDEFINED(a,len) VALGRIND_MAKE_MEM_UNDEFINED(a,len)
 # define MEM_NOACCESS(a,len) VALGRIND_MAKE_MEM_NOACCESS(a,len)