TBR: i#1273 use drmgr everywhere: update modxfer* to use drmgr

Commit log for first patchset:
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i#1273 use drmgr everywhere: update modxfer* to use drmgr

Updates the modxfer and modxfer_app2lib samples to use drmgr's analysis and
insertion events.  This also requires using drreg for modxfer due to its
use of drx_insert_counter_update().

Of note is that we have to restore app values prior to
dr_insert_mbr_instrumentation().  This hit a bug where
drreg_restore_app_values() doesn't skip segment regs, which we also fix
here.
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[bruening, 2017-01-30 06:24:09]

Committed as
https://github.com/DynamoRIO/dynamorio/commit/4891c7257d16e5e0e918b0918b1bdb2...

Final commit log: 
---------------
i#1273 use drmgr everywhere: update modxfer* to use drmgr

Updates the modxfer and modxfer_app2lib samples to use drmgr's analysis and
insertion events.  This also requires using drreg for modxfer due to its
use of drx_insert_counter_update().

Of note is that we have to restore app values prior to
dr_insert_mbr_instrumentation().  This hit a bug where
drreg_restore_app_values() doesn't skip segment regs, which we also fix
here.

Review-URL: https://codereview.appspot.com/312360043
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