On Linux with pthread library spdlog causes an SIGABORT and crashes
the application in case it catches a thread specific cancellation
exception in a critical execution phase while in a try/catch block
in spdlog/detail/logger_impl.h

The exception is caught by some general catch(...) clause where
it is NOT rethrown.

However rethrowing these kind of exception is mandatory, otherwise
an abort will be caused by the glibc.

Support for printf-style logging

* tests updated for printf style
* tests makefile support printf style

Fix SPDLOG_WCHAR_TO_UTF8_SUPPORT wchar_t logging

add formatter for unix epoch time in seconds.

Compiler-dependent line numbering

Feature/improve cmake lists

* support CMake user registry package registration
* use GNUInstallDirs to set installation firectories
* use spdlog namespace in both build and install interfaces

SPDLOG_BUILD_TESTING now depends on BUILD_TESTING

I encountered an issue when using spdlog through add_subdirectory.
Since SPDLOG_BUILD_TESTING is ON by default, it now adds tests to my project, even if BUILD_TESTING (the official CTest variable) is set to OFF.
cmake_dependent_option makes it so that if someone enables BUILD_TESTING then SPDLOG_BUILD_TESTING will be set to ON by default.
This way one can disable all external tests by setting BUILD_TESTING before using add_subdirectory and then setting it back to its original value.
The only change for those using the library directly is that they now use BUILD_TESTING instead of SPDLOG_BUILD_TESTING when configuring.

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