Minor changes and elimination of definitions

doc/Type/Str.pod6

@@ -195,12 +195,14 @@ ASCII string: could not encode codepoint 222> will be issued.
 
 =head2 routine index
 
-    multi sub    index(Cool $s, Str:D $needle, Cool $startpos = 0 --> Int)
-    multi method index(Cool $needle, Cool $startpos = 0 --> Int)
+    multi method index(Str:D: Cool:D $needle --> Int:D)
+    multi method index(Str:D: Str:D $needle --> Int:D)
+    multi method index(Str:D: Cool:D $needle, Cool:D $pos --> Int:D)
+    multi method index(Str:D: Str:D $needle, Int:D $pos --> Int:D)
 
-Searches for C<$needle> in the string starting from C<$startpos>. It returns
-the offset into the string where C<$needle> was found, and C<Nil> if it was not
-found.
+Searches for C<$needle> in the string starting from C<$pos> (if present). It
+returns the offset into the string where C<$needle> was found, and C<Nil> if it
+was not found.
 
 Examples:
 
@@ -212,6 +214,9 @@ Examples:
 
     say index("Camelia is a butterfly", "Onion").defined ?? 'OK' !! 'NOT'; # OUTPUT: «NOT␤»
 
+Other forms of index, including a sub, are
+L<inherited from C<Cool>|/type/Cool#routine_index>. Check them there.
+
 =head2 routine rindex
 
     multi sub    rindex(Str:D $haystack, Str:D $needle, Int $startpos = $haystack.chars --> Int)