strings.Split: make the default to split all.

Change the signature of Split to have no count,
assuming a full split, and rename the existing
Split with a count to SplitN.
Do the same to package bytes.
Add a gofix module.

R=adg, dsymonds, alex.brainman, rsc
CC=golang-dev
https://golang.org/cl/4661051

src/pkg/strings/strings.go

@@ -198,24 +198,38 @@ func genSplit(s, sep string, sepSave, n int) []string {
 	return a[0 : na+1]
 }
 
-// Split slices s into substrings separated by sep and returns a slice of
+// SplitN slices s into substrings separated by sep and returns a slice of
+// the substrings between those separators.
+// If sep is empty, SplitN splits after each UTF-8 sequence.
+// The count determines the number of substrings to return:
+//   n > 0: at most n substrings; the last substring will be the unsplit remainder.
+//   n == 0: the result is nil (zero substrings)
+//   n < 0: all substrings
+func SplitN(s, sep string, n int) []string { return genSplit(s, sep, 0, n) }
+
+// SplitAfterN slices s into substrings after each instance of sep and
+// returns a slice of those substrings.
+// If sep is empty, SplitAfterN splits after each UTF-8 sequence.
+// The count determines the number of substrings to return:
+//   n > 0: at most n substrings; the last substring will be the unsplit remainder.
+//   n == 0: the result is nil (zero substrings)
+//   n < 0: all substrings
+func SplitAfterN(s, sep string, n int) []string {
+	return genSplit(s, sep, len(sep), n)
+}
+
+// Split slices s into all substrings separated by sep and returns a slice of
 // the substrings between those separators.
 // If sep is empty, Split splits after each UTF-8 sequence.
-// The count determines the number of substrings to return:
-//   n > 0: at most n substrings; the last substring will be the unsplit remainder.
-//   n == 0: the result is nil (zero substrings)
-//   n < 0: all substrings
-func Split(s, sep string, n int) []string { return genSplit(s, sep, 0, n) }
+// It is equivalent to SplitN with a count of -1.
+func Split(s, sep string) []string { return genSplit(s, sep, 0, -1) }
 
-// SplitAfter slices s into substrings after each instance of sep and
+// SplitAfter slices s into all substrings after each instance of sep and
 // returns a slice of those substrings.
-// If sep is empty, Split splits after each UTF-8 sequence.
-// The count determines the number of substrings to return:
-//   n > 0: at most n substrings; the last substring will be the unsplit remainder.
-//   n == 0: the result is nil (zero substrings)
-//   n < 0: all substrings
-func SplitAfter(s, sep string, n int) []string {
-	return genSplit(s, sep, len(sep), n)
+// If sep is empty, SplitAfter splits after each UTF-8 sequence.
+// It is equivalent to SplitAfterN with a count of -1.
+func SplitAfter(s, sep string) []string {
+	return genSplit(s, sep, len(sep), -1)
 }
 
 // Fields splits the string s around each instance of one or more consecutive white space