fix count-matches and add unit test for it

basis/regexp/regexp-tests.factor

@@ -283,6 +283,12 @@ IN: regexp-tests
 [ { "ABC" "DEF" "GHI" } ]
 [ "1ABC2DEF3GHI4" R/ [A-Z]+/ all-matches [ >string ] map ] unit-test
 
+[ 3 ]
+[ "1ABC2DEF3GHI4" R/ [A-Z]+/ count-matches ] unit-test
+
+[ 0 ]
+[ "123" R/ [A-Z]+/ count-matches ] unit-test
+
 [ "1.2.3.4" ]
 [ "1ABC2DEF3GHI4JK" R/ [A-Z]+/ "." re-replace ] unit-test
 

basis/regexp/regexp.factor

@@ -73,7 +73,7 @@ IN: regexp
     [ dup ] swap '[ _ next-match ] [ ] produce nip harvest ;
 
 : count-matches ( string regexp -- n )
-    all-matches length 1- ;
+    all-matches length ;
 
 : initial-option ( regexp option -- regexp' )
     over options>> conjoin ;