strings,bytes: use inlineable function trampolines instead of linkname

Cleans things up quite a bit.

There's still a few more, like runtime.cmpstring, which might also
be worth fixing.

Change-Id: Ide18dd621efc129cc686db223f47fa0b044b5580
Reviewed-on: https://go-review.googlesource.com/c/148578
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

src/bytes/bytes.go

@@ -12,6 +12,13 @@ import (
 	"unicode/utf8"
 )
 
+// Equal returns a boolean reporting whether a and b
+// are the same length and contain the same bytes.
+// A nil argument is equivalent to an empty slice.
+func Equal(a, b []byte) bool {
+	return bytealg.Equal(a, b)
+}
+
 func equalPortable(a, b []byte) bool {
 	if len(a) != len(b) {
 		return false
@@ -24,6 +31,13 @@ func equalPortable(a, b []byte) bool {
 	return true
 }
 
+// Compare returns an integer comparing two byte slices lexicographically.
+// The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
+// A nil argument is equivalent to an empty slice.
+func Compare(a, b []byte) int {
+	return bytealg.Compare(a, b)
+}
+
 // explode splits s into a slice of UTF-8 sequences, one per Unicode code point (still slices of bytes),
 // up to a maximum of n byte slices. Invalid UTF-8 sequences are chopped into individual bytes.
 func explode(s []byte, n int) [][]byte {
@@ -83,6 +97,11 @@ func ContainsRune(b []byte, r rune) bool {
 	return IndexRune(b, r) >= 0
 }
 
+// IndexByte returns the index of the first instance of c in b, or -1 if c is not present in b.
+func IndexByte(b []byte, c byte) int {
+	return bytealg.IndexByte(b, c)
+}
+
 func indexBytePortable(s []byte, c byte) int {
 	for i, b := range s {
 		if b == c {