Update comment

m-dict.h

@@ -1725,6 +1725,7 @@ typedef enum {
     size_t size;							\
     /* Get the size which will allow to fit this capacity */		\
     size = m_core_roundpow2 (capacity * (1.0 / coeff_up));		\
+    /* Test for overflow of the computation */                          \
     if (M_UNLIKELY (size < capacity)) {					\
       M_MEMORY_FULL((size_t)-1);					\
     }									\