Nintendo switch support (#8069)

* Add config section for Nintendo Switch
* Add compiler configuration for Nintendo Switch and it's CPU
* Add specific lib code for Nintendo Switch
* Add GC support for Nintendo Switch
* Update changelog for Nintendo Switch
* Update changelog with more info about fixed paths
* Cleaned up GC memory management a bit
* Relocate docs for Switch
* Rename aarch64NoneElfGcc to nintendoSwitchGCC
* Remove armv8a57
* Fix installer.ini
* Reuse code in linux and amd64
* Add posix defs for nintendo switch
* Add more defined sections for nintendo switch
* Remove old comment
* Add what's not supported for Nintendo Switch docs
* Make nintendoswitch == posix
* Remove DEVKITPRO references from nim.cfg
* Make PR extccomp changes
* Remove Result type alias
* Add separate switch consts file
* Update docs for nintendo switch
* Fix travis errors with undefined consts and add correct wait.h procs

lib/system/platforms.nim

@@ -37,7 +37,7 @@ type
     none, dos, windows, os2, linux, morphos, skyos, solaris,
     irix, netbsd, freebsd, openbsd, aix, palmos, qnx, amiga,
     atari, netware, macos, macosx, haiku, android, js, nimVM,
-    standalone
+    standalone, nintendoswitch
 
 const
   targetOS* = when defined(windows): OsPlatform.windows
@@ -64,6 +64,7 @@ const
               elif defined(js): OsPlatform.js
               elif defined(nimVM): OsPlatform.nimVM
               elif defined(standalone): OsPlatform.standalone
+              elif defined(nintendoswitch): OsPlatform.nintendoswitch
               else: OsPlatform.none
     ## the OS this program will run on.