exp/cookiejar: make cookie sorting deterministic.

Re-enable TestUpdateAndDelete, TestExpiration, TestChromiumDomain and
TestChromiumDeletion on Windows.

Sorting of cookies with same path length and same creation
time is done by an additional seqNum field.
This makes the order in which cookies are returned in Cookies
deterministic, even if the system clock is manipulated or on
systems with a low-resolution clock.

The tests now use a synthetic time: This makes cookie testing
reliable in case of bogus system clocks and speeds up the
expiration tests.

R=nigeltao, alex.brainman, dave
CC=golang-dev
https://codereview.appspot.com/7323063

Committer: Nigel Tao <nigeltao@golang.org>
misc/vim: update installation instructions to work better with some Linux distributions.

Fixes issue 3308.

R=golang-dev, minux.ma
CC=golang-dev
https://codereview.appspot.com/7301086
runtime/debug: make TestFreeOSMemory repeatable
Fixes issue 4835.

R=golang-dev, fullung
CC=golang-dev
https://codereview.appspot.com/7319050
cmd/6c, cmd/8c: cut stack frames by about half

The routine that adds an automatic to the stack was
adding ptrsize-1 to the size before rounding up.
That addition would only make sense to turn a round down
into a round up. Before a round up, it just wastes a word.

The effect was that a 6c function with one local and
one two-word function call used (8+8)+(16+8) = 40 bytes
instead of 8+16 = 24 bytes.

The wasted space mostly didn't matter, but one place where
it does matter is when trying to stay within the 128-byte
total frame constraint for #pragma textflag 7 functions.

This only affects the C compilers, not the Go compilers.

5c already had correct code, which is now copied to 6c and 8c.

R=ken2
CC=golang-dev
https://codereview.appspot.com/7303099
cmd/6c: fix build

copy+paste error while cleaning up CL 7303099 before submit

R=ken2
CC=golang-dev
https://codereview.appspot.com/7308104
runtime: preparation for non-Go threads running Go code

* Handle p==nil in signalstack by setting SS_DISABLE flag.
* Make minit only allocate a signal g if there's not one already.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/7323072