Refactor colour handling to prepare for per-reporter colour modes

This includes always compiling the ANSI and None colour
implementations, as they don't need to touch any platform
specific APIs, and removing their respective compile-time
configuration options.

Because the Win32 colour implementation requires Win32-specific
APIs, it is still hidden behind a compile-time toggle,
`CATCH_CONFIG_COLOUR_WIN32` (renamed from `..._COLOUR_WINDOWS`).

The commandline options for colours were also changed. The
option now uses different name, and allows to select between
different implementations, rather than changing whether
the compiled-in colour implementation is used through
"yes/no/default" options.

src/catch2/internal/catch_compiler_capabilities.hpp

@@ -116,7 +116,6 @@
 
 #ifdef __OS400__
 #       define CATCH_INTERNAL_CONFIG_NO_POSIX_SIGNALS
-#       define CATCH_CONFIG_COLOUR_NONE
 #endif
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -164,7 +163,7 @@
 // Universal Windows platform does not support SEH
 // Or console colours (or console at all...)
 #  if defined(WINAPI_FAMILY) && (WINAPI_FAMILY == WINAPI_FAMILY_APP)
-#    define CATCH_CONFIG_COLOUR_NONE
+#    define CATCH_INTERNAL_CONFIG_NO_COLOUR_WIN32
 #  else
 #    define CATCH_INTERNAL_CONFIG_WINDOWS_SEH
 #  endif
@@ -206,7 +205,7 @@
 #if defined(UNDER_RTSS) || defined(RTX64_BUILD)
     #define CATCH_INTERNAL_CONFIG_NO_WINDOWS_SEH
     #define CATCH_INTERNAL_CONFIG_NO_ASYNC
-    #define CATCH_CONFIG_COLOUR_NONE
+    #define CATCH_INTERNAL_CONFIG_NO_COLOUR_WIN32
 #endif
 
 #if !defined(_GLIBCXX_USE_C99_MATH_TR1)
@@ -358,4 +357,12 @@
 #define CATCH_CONFIG_TRADITIONAL_MSVC_PREPROCESSOR
 #endif
 
+#if defined( CATCH_PLATFORM_WINDOWS ) &&       \
+    !defined( CATCH_CONFIG_COLOUR_WIN32 ) && \
+    !defined( CATCH_CONFIG_NO_COLOUR_WIN32 ) && \
+    !defined( CATCH_INTERNAL_CONFIG_NO_COLOUR_WIN32 )
+#    define CATCH_CONFIG_COLOUR_WIN32
+#endif
+
+
 #endif // CATCH_COMPILER_CAPABILITIES_HPP_INCLUDED