Fix compilation when INTERNAL_LOOP_NTIMES is not set and create avx512 directory

Signed-off-by: Rafael Ravedutti <rafaelravedutti@gmail.com>

src/includes/parameter.h

@@ -29,6 +29,11 @@
 #define MD_FLOAT double
 #endif
 
+// Number of times to compute the most internal loop
+#ifndef INTERNAL_LOOP_NTIMES
+#define INTERNAL_LOOP_NTIMES 1
+#endif
+
 typedef struct {
     MD_FLOAT epsilon;
     MD_FLOAT sigma6;