__SIGFUNC__ no longer default for Windows. __PRETTY__FUNCTION no longer default for gcc/clang

[KjellKod]

SIGFUNC no longer default for Windows, It has to be explicitly picked through CMAKE option

[KjellKod]

1. Example output with PRETTY_FUNCTION:OFF (which is default) from examples/g2log-FATAL-sigsegv

INFO [main_sigsegv.cpp->tryToKillWithAccessingIllegalPointer:51]

2. example output with PRETTY_FUNCTION:ON from examples/g3log-FATAL-sigsegv

// formatted for readability
INFO 
[main_sigsegv.cpp->
void example_fatal::tryToKillWithAccessingIllegalPointer(std::unique_ptr<std::string>):51]

template arguments are expanded.

3. SIGFUNC no longer default for Windows, It has to be explicitly picked through CMAKE option

[KjellKod]

This is easier to read if you look at the plain file rather than the diff

[KjellKod]

circleCI runs PRETTY_FUNCTION:ON and gitaction runs PRETTY_FUNCTION:OFF

[KjellKod]

__PRETTY_FUNCTION__ and __FUNCSIG__ were not used before #424

This PR makes sure that the previous default is still __FUNCTION__ while __PRETTY_FUNCTION__ and __FUNCSIG__ can be activated using CMake options.