all: fix some problematic comments

Change-Id: Ia110d19fe5ff3adc8bbf86dd2112f9702164d495
Reviewed-on: https://go-review.googlesource.com/c/go/+/475515
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

src/crypto/hmac/hmac.go

@@ -35,7 +35,7 @@ import (
 // opad = 0x5c byte repeated for key length
 // hmac = H([key ^ opad] H([key ^ ipad] text))
 
-// Marshalable is the combination of encoding.BinaryMarshaler and
+// marshalable is the combination of encoding.BinaryMarshaler and
 // encoding.BinaryUnmarshaler. Their method definitions are repeated here to
 // avoid a dependency on the encoding package.
 type marshalable interface {

src/runtime/mfixalloc.go

@@ -13,7 +13,7 @@ import (
 	"unsafe"
 )
 
-// FixAlloc is a simple free-list allocator for fixed size objects.
+// fixalloc is a simple free-list allocator for fixed size objects.
 // Malloc uses a FixAlloc wrapped around sysAlloc to manage its
 // mcache and mspan objects.
 //

src/runtime/mspanset.go

@@ -322,7 +322,7 @@ func (p *spanSetBlockAlloc) free(block *spanSetBlock) {
 	p.stack.push(&block.lfnode)
 }
 
-// haidTailIndex represents a combined 32-bit head and 32-bit tail
+// headTailIndex represents a combined 32-bit head and 32-bit tail
 // of a queue into a single 64-bit value.
 type headTailIndex uint64