Both callers of ChanRead() have simlar epilogs.  Shift that into ChanRead
and refactor.
Documentation header for ChanRead()
io-34.21 - fix bugs in normally skipped test.
io-35.18b - knownBug is not buggy on this branch.
Fixup ChanRead() header.  Note (dstSize > 0) precondition.
Restore default suppression of large file test.
Convert "impossible" test to a "knownBug" test.  Exposes a segfault!
Added comment explaining the "knownBug"
Correct namespace bugs in normally skipped tests.
Constrain them as "knownBug" rather than "unknownFailure".
missing declaration
Salvaged what was left of value in the dgp-read-bytes-detour branch.
Refactored much management of the BLOCKED and EOF flags into ChanRead()
then began repairing some of the logic about them.
Tests iogt-2.* now fail because they've been crafted as experiments recording
the fine detail of reflected channel driver calls, and fixing the management
of channel flags is changing that.
Rework Tcl_ReadRaw() mostly taking things out of the loop that never repeat.
Refactored much management of the BLOCKED and EOF flags into ChanRead() then
began repairing some of the logic about them. Tests iogt-2.* now fail because
they've been crafted as experiments recording the fine detail of reflected
channel driver calls, and fixing the management of channel flags is changing
that. zlib-8.5 also needed adjustment to reflect that an EOF set must come
with an empty string read when flags are functioning properly.
merge 8.5
merge trunk
Push the setting and clearing of CHANNEL_BLOCKED flag to the more inner
parts of the channel read machinery.
merge 8.5
merge trunk
Move the resets and testings of the BLOCKED flag to where they make more sense.
Improved use of EOF state to avoid worthless allocations.
Merge flag changes. - Wow, no trouble with [chan push] demonstrated.