i#1114 JIT optimization: generalize flush/synch with per-thread callback

Commit log for first patchset:
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i#1114 JIT optimization: generalize flush/synch with per-thread callback

Generalize the 3-stage synch/flush sequence by adding
an alternative stage 1 that takes a callback function,
which is invoked per thread after synch.
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[Byron, 2016-01-20 12:23:27]

This CL mostly moves existing lines around to make the per-thread callback
possible. It should be equivalent to TOT for current callers--it passes
pre-commit on Linux and Windows, and the long suite on Linux.

https://codereview.appspot.com/283090043/diff/1/core/fragment.c
File core/fragment.c (right):

https://codereview.appspot.com/283090043/diff/1/core/fragment.c#newcode54
core/fragment.c:54: #include "jit_opt.h"
Not really necessary for this CL. I removed it in my local just now.

https://codereview.appspot.com/283090043/diff/1/core/fragment.c#newcode5717
core/fragment.c:5717: 
Accidental blank line--will remove it.

https://codereview.appspot.com/283090043/diff/1/core/fragment.c#newcode6353
core/fragment.c:6353: flush_base = base;
Instead of making these static, they could be passed to the callback. Though in
general the caller can keep such things as static.

[bruening, 2016-01-22 18:07:00]

The diff is not easy to read with all of the moved code so I hope there are
enough tests to stress it (prob not in suite -- ideally this will be tested on
some DGC-heavy apps).  LGTM

https://codereview.appspot.com/283090043/diff/1/core/fragment.c
File core/fragment.c (left):

https://codereview.appspot.com/283090043/diff/1/core/fragment.c#oldcode6417
core/fragment.c:6417: /* restore, since won't be restored in
vm_area_flush_fragments */
this comment was lost?

[Byron, 2016-01-24 11:12:47]

Committed as
https://github.com/DynamoRIO/dynamorio/commit/1445c54dac0628cc6cb729b2a9c8c86...

Final commit log: 
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i#1114 JIT optimization: generalize flush/synch with per-thread callback

Generalize the 3-stage synch/flush sequence by adding
an alternative stage 1 that takes a callback function,
which is invoked per thread after synch.

Review-URL: https://codereview.appspot.com/283090043
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