Add support for PlayStation platforms (#2562)

* Add new `CATCH_CONFIG` option for using `std::getenv`, because PS does not support env vars
* Add PS to platforms that have disabled posix signals.
* Small workaround for PS toolchain bug that prevents it from compiling `std::set` with lambda based comparator.

docs/configuration.md

@@ -155,13 +155,20 @@ by using `_NO_` in the macro, e.g. `CATCH_CONFIG_NO_CPP17_UNCAUGHT_EXCEPTIONS`.
     CATCH_CONFIG_USE_ASYNC                  // Force parallel statistical processing of samples during benchmarking
     CATCH_CONFIG_ANDROID_LOGWRITE           // Use android's logging system for debug output
     CATCH_CONFIG_GLOBAL_NEXTAFTER           // Use nextafter{,f,l} instead of std::nextafter
+    CATCH_CONFIG_GETENV                     // System has a working `getenv`
 
 > [`CATCH_CONFIG_ANDROID_LOGWRITE`](https://github.com/catchorg/Catch2/issues/1743) and [`CATCH_CONFIG_GLOBAL_NEXTAFTER`](https://github.com/catchorg/Catch2/pull/1739) were introduced in Catch2 2.10.0
 
+> `CATCH_CONFIG_GETENV` was [introduced](https://github.com/catchorg/Catch2/pull/2562) in Catch2 X.Y.Z
+
 Currently Catch enables `CATCH_CONFIG_WINDOWS_SEH` only when compiled with MSVC, because some versions of MinGW do not have the necessary Win32 API support.
 
 `CATCH_CONFIG_POSIX_SIGNALS` is on by default, except when Catch is compiled under `Cygwin`, where it is disabled by default (but can be force-enabled by defining `CATCH_CONFIG_POSIX_SIGNALS`).
 
+`CATCH_CONFIG_GETENV` is on by default, except when Catch2 is compiled for
+platforms that lacks working `std::getenv` (currently Windows UWP and
+Playstation).
+
 `CATCH_CONFIG_WINDOWS_CRTDBG` is off by default. If enabled, Windows's
 CRT is used to check for memory leaks, and displays them after the tests
 finish running. This option only works when linking against the default