use fully qualified names for hash interfaces

Fixes #38.

R=r1, r
https://golang.org/cl/152072

src/pkg/crypto/md5/md5.go

@@ -38,7 +38,7 @@ func (d *digest) Reset() {
 	d.len = 0;
 }
 
-// New returns a Hash computing the SHA1 checksum.
+// New returns a hash.Hash computing the SHA1 checksum.
 func New() hash.Hash {
 	d := new(digest);
 	d.Reset();

src/pkg/crypto/sha1/sha1.go

@@ -40,7 +40,7 @@ func (d *digest) Reset() {
 	d.len = 0;
 }
 
-// New returns a Hash computing the SHA1 checksum.
+// New returns a new hash.Hash computing the SHA1 checksum.
 func New() hash.Hash {
 	d := new(digest);
 	d.Reset();

src/pkg/hash/adler32/adler32.go

@@ -32,7 +32,7 @@ type digest struct {
 
 func (d *digest) Reset()	{ d.a, d.b = 1, 0 }
 
-// New returns a new Hash32 computing the Adler-32 checksum.
+// New returns a new hash.Hash32 computing the Adler-32 checksum.
 func New() hash.Hash32 {
 	d := new(digest);
 	d.Reset();

src/pkg/hash/crc32/crc32.go

@@ -60,11 +60,11 @@ type digest struct {
 	tab	*Table;
 }
 
-// New creates a new Hash computing the CRC-32 checksum
+// New creates a new hash.Hash32 computing the CRC-32 checksum
 // using the polynomial represented by the Table.
 func New(tab *Table) hash.Hash32	{ return &digest{0, tab} }
 
-// NewIEEE creates a new Hash computing the CRC-32 checksum
+// NewIEEE creates a new hash.Hash32 computing the CRC-32 checksum
 // using the IEEE polynomial.
 func NewIEEE() hash.Hash32	{ return New(IEEETable) }