Release 1.89.

Fix ANSICON environment variable
Creating a console handle in `set_ansicon` was assumed to succeed, but
that is not the case when there is no console (if the process was
started detached or freed its console).  This left the console info
uninitialised, causing my `printf` replacement to get stuck in a loop.
Resolves #127.

Fix crash when some programs start
A few functions that are hooked are not imported, so testing if my
import was already hooked would fail.
SetCurrentConsoleFontEx should have been hooked, but wasn't.

Fixes
Unhook on terminate, to properly exit (Vista CMD.EXE and a MinGW-built
ansicon.exe would seem to exit okay, but the exit code was wrong).
Fixes #123.
Verify the DLL exists prior to injection.  With the DLL now being added
to the import table, failing to find it would prevent the process itself
from loading.

Preserve last error
Hooked functions that failed and logged debug messages were causing an
incorrect last error to be set.

Release v1.84

Create the flush thread on first use
Some processes just return from the entry point; this only exits the
thread, not the process.  It seems that when ANSICON created its flush
thread in DllMain, that became the primary thread, so when the entry
point returned the process was still waiting for the flush thread to
exit.  Creating the flush thread the first time it is used avoids this
problem, letting the process exit.

Release v1.82

Release 1.81

Flush when idle
Flush 15ms after the last write.  This would typically be needed to show
a progress display.