Submodule libxmp inconsistency

[1vanK]

All submodules have a name external/....

Git files: .git\modules\external\...

.gitmodules:

[submodule "external/SDL"]
	path = external/SDL
	url = https://github.com/libsdl-org/SDL.git
	branch = main
[submodule "external/flac"]
	path = external/flac
	url = https://github.com/libsdl-org/flac.git
	branch = 1.3.4-SDL
...

---

Only libxmp have name without external.

Git files: .git\modules\libxmp

.gitmodules:

[submodule "libxmp"]
	path = external/libxmp
	url = https://github.com/libsdl-org/libxmp.git
	branch = 4.6.x-SDL