api: update next.txt

Change-Id: I0ea74dc1b11fad8ded9e649a3c1e4213ea6639b8
Reviewed-on: https://go-review.googlesource.com/20974
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

api/next.txt

+pkg crypto/tls, type Config struct, DynamicRecordSizingDisabled bool
+pkg go/build, type Package struct, CgoFFLAGS []string
+pkg go/build, type Package struct, FFiles []string
+pkg go/doc, type Example struct, Unordered bool
+pkg net/http/httptest, method (*ResponseRecorder) Trailers() http.Header
+pkg net/url, type URL struct, ForceQuery bool
+pkg os/user, func LookupGroup(string) (*Group, error)
+pkg os/user, func LookupGroupId(string) (*Group, error)
+pkg os/user, method (*User) GroupIds() ([]string, error)
+pkg os/user, method (UnknownGroupError) Error() string
+pkg os/user, method (UnknownGroupIdError) Error() string
+pkg os/user, type Group struct
+pkg os/user, type Group struct, Gid string
+pkg os/user, type Group struct, Name string
+pkg os/user, type UnknownGroupError string
+pkg os/user, type UnknownGroupIdError string
+pkg runtime, func CallersFrames([]uintptr) *Frames
+pkg runtime, method (*Frames) Next() (Frame, bool)
+pkg runtime, type Frame struct
+pkg runtime, type Frame struct, Entry uintptr
+pkg runtime, type Frame struct, File string
+pkg runtime, type Frame struct, Func *Func
+pkg runtime, type Frame struct, Function string
+pkg runtime, type Frame struct, Line int
+pkg runtime, type Frame struct, PC uintptr
+pkg runtime, type Frames struct
+pkg testing, type InternalExample struct, Unordered bool