doc, api: add type Srcset string change to go1.10 notes and API

Change-Id: I13afaa894292bd566510b40a5e4bbbe4d72d4d08
Reviewed-on: https://go-review.googlesource.com/87395
Reviewed-by: Ian Lance Taylor <[email protected]>

net/http/httputil: remove redundant call of setBody in test

Change-Id: I5a38200b9e050b484ec39f47c637e651e237390d
Reviewed-on: https://go-review.googlesource.com/82536
Reviewed-by: Brad Fitzpatrick <[email protected]>
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

api: promote next to go1.10

Change-Id: I2a4347540ecb94a9f124a228dc31452620ab0645

os: add UserCacheDir

Adds a function that returns an OS-dependent location
for user-specific cache data.

Fixes golang#22536

Change-Id: Ifff015452494571ad357fa2d945d66a5992c751d

[release-branch.go1.9] go1.9.2

Change-Id: Idb72e9f562887680e0b287649a4ae1325d7e3eb5
Reviewed-on: https://go-review.googlesource.com/71271
Run-TryBot: Russ Cox <[email protected]>
Reviewed-by: Chris Broadfoot <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

[release-branch.go1.8] go1.8.5

Change-Id: I7c6cf169e84329a31d2d9dc4c52d5c29e80482c9
Reviewed-on: https://go-review.googlesource.com/71350
Run-TryBot: Russ Cox <[email protected]>
Reviewed-by: Chris Broadfoot <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

[release-branch.go1.8] go1.8.5

TESTING: go1.8.5rc5

DO NOT REVIEW

Change-Id: I7c6cf169e84329a31d2d9dc4c52d5c29e80482c9

[release-branch.go1.8] go1.8.5

TESTING: go1.8.5rc4

DO NOT REVIEW

Change-Id: I7c6cf169e84329a31d2d9dc4c52d5c29e80482c9

[release-branch.go1.9] go1.9.1

Change-Id: I711b38738a7f6fade42a2821908234940f3cf280
Reviewed-on: https://go-review.googlesource.com/68233
Reviewed-by: Russ Cox <[email protected]>

[release-branch.go1.8] go1.8.4

Change-Id: Iae6c1ccd1e42656fa5a57d6367e43085143cd590
Reviewed-on: https://go-review.googlesource.com/68234
Reviewed-by: Russ Cox <[email protected]>