unsafe: update doc

changeset: 8812:3fb3e88d5aa8
gc: unsafe.Alignof, unsafe.Offsetof, unsafe.Sizeof now return uintptr

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4951051

src/pkg/unsafe/unsafe.go

@@ -24,17 +24,17 @@ type Pointer *ArbitraryType
 // Sizeof returns the size in bytes occupied by the value v.  The size is that of the
 // "top level" of the value only.  For instance, if v is a slice, it returns the size of
 // the slice descriptor, not the size of the memory referenced by the slice.
-func Sizeof(v ArbitraryType) int
+func Sizeof(v ArbitraryType) uintptr
 
 // Offsetof returns the offset within the struct of the field represented by v,
 // which must be of the form struct_value.field.  In other words, it returns the
 // number of bytes between the start of the struct and the start of the field.
-func Offsetof(v ArbitraryType) int
+func Offsetof(v ArbitraryType) uintptr
 
 // Alignof returns the alignment of the value v.  It is the maximum value m such
 // that the address of a variable with the type of v will always always be zero mod m.
 // If v is of the form obj.f, it returns the alignment of field f within struct object obj.
-func Alignof(v ArbitraryType) int
+func Alignof(v ArbitraryType) uintptr
 
 // Typeof returns the type of an interface value, a runtime.Type.
 func Typeof(i interface{}) (typ interface{})