Change ambiguous and unknown string macros's value

To fit issue #3250 the macros values were changed.
Char n°0 for ambiguous and char n°1 for unknown K-mer.

algo/core/kmeraffect.h

@@ -170,8 +170,8 @@ bool operator!=(const KmerAffect &a1, const KmerAffect &a2);
 ostream &operator<<(ostream &os, const KmerAffect &kmer);
 
 #define AFFECT_NOT_UNKNOWN_SYMBOL "*"
-#define AFFECT_AMBIGUOUS_SYMBOL "?"
-#define AFFECT_UNKNOWN_SYMBOL "_"
+#define AFFECT_AMBIGUOUS_SYMBOL "\0"
+#define AFFECT_UNKNOWN_SYMBOL "\1"
 #define AFFECT_AMBIGUOUS_CHAR (AFFECT_AMBIGUOUS_SYMBOL[0])
 #define AFFECT_UNKNOWN_CHAR (AFFECT_UNKNOWN_SYMBOL[0])