overlapped read boosts performance

use overlapped read to efficiently wait until there is data available

this boosts performance considerably when the write to stderr is done in
short bursts with very little data.
for example, run:
test.bat 11 22 1000

new mode: now can redirect stderr in the current console

usually errcolor will create a new console process with its stderr already redirected.

with the new mode, errcolor can also redirect stderr in an existing console without running another process or a subshell.

see "attach-errcolor-to-current-console.bat" in "tests" directory for an example.

basic command line support

usage: [-c ] [-e ]

v0.6

ready enough to use

first release

v0.5

Add screenshot