* Remove unmotivated check preventing texture ini creation on mobile.
Fixes#15644
* Show a "toast" message on platforms that don't support opening a text editor, when you try to create/open a texture ini file.
* Avoid the need to ifdef around calls to SystemToast
* UWP buildfix (and some warning fixes).
And possibly libretro fix
* Rename for a bit more consistency
Still left some ifdefs because of System_InputBoxGetString(), but
hopefully we can move away from them. Some devices (like SDL) may only
optionally have a keyboard, so it's a runtime check.
This will disappear in future Android versions but can be useful for
older devices.
Fixes (or at least tries to) #10199, at least for some devices.
Might help #13827 ?
Tested on Pocophone F1.
