Fix spelling.

doc/ISSUES.org

@@ -11,7 +11,7 @@ Check if it will be better as intrusive or non-intrusive container.
 To test if a bucket is empty or not, a bitfield can be used to check if
 the bit associated to the bucket is set or not. To get the highest bucket
 non empty, we can perform a CLZ of the bitset, which shall be much faster than
-perming a linear search of the buckets (algorithm complexity is the same,
+performing a linear search of the buckets (algorithm complexity is the same,
 except that we can scan 64 entries at a time).
 
 Check if we can use BITSET, or introduce fixed size BITSET or use ad-hock