Issue-488: warning for missing enumeration value

readme: Add Gentoo package name

Background color unchanged

Keep the background color unchaged on Windows console when using colored loggers.

Added TRACE/DEBUG_IF macro definitions when TRACE/DEBUG_ON aren't defined

fixed length and upper case log level tags(after suggestion)

code formatting (astyle and dos2unix)

it aims to solve the issue #467

Add set_color to ansicolor_sink

It is now possible again to set the color in the ansicolor_sink with set_color

More meaningful thread id for OSX

conditional logging

Add create_async factory functions for async loggers

Fix for MinGW error: 'There are no arguments that depend on a template parameter'

Signed-off-by: Remigiusz Kołłątaj <remigiusz.kollataj@gmail.com>

UTC Time

use if statement instead of switch (changes of adding new time specifications outside of standard are probably unlikely anyhow)
pattern_time -> pattern_time_type
ptime variable name -> pattern_time variable name
make sure four spaces used, not tabs

_pattern was never set... but it was also never used. Intentional by @gabime, or a reflection of a refactor with some data member left behind?