Changed multi-line C comments into another style.

The left side doesn't look unbalanced.

src/ca65/feature.h

@@ -80,14 +80,14 @@ typedef enum {
 
 feature_t FindFeature (const StrBuf* Key);
 /* Find the feature in a table and return the corresponding enum value. If the
- * feature is invalid, return FEAT_UNKNOWN.
- */
+** feature is invalid, return FEAT_UNKNOWN.
+*/
 
 feature_t SetFeature (const StrBuf* Key);
 /* Find the feature and set the corresponding flag if the feature is known.
- * In any case, return the feature found. An invalid Key will return
- * FEAT_UNKNOWN.
- */
+** In any case, return the feature found. An invalid Key will return
+** FEAT_UNKNOWN.
+*/