gnu: Delete mono and dependent packages.

Fixes <https://issues.guix.gnu.org/55026>.

* gnu/packages/mono.scm: Delete file.
* gnu/packages/patches/mono-mdoc-timestamping.patch: Likewise.
* gnu/local.mk (GNU_SYSTEM_MODULES): De-register module file.
(dist_patch_DATA): Re-register patch file.
* gnu/packages/game-development.scm (fna): Delete variable.
* gnu/packages/gl.scm (mojoshader-cs): Likewise.
* gnu/packages/sdl.scm (sdl2-cs): Likewise.

gnu/packages/game-development.scm

@@ -87,7 +87,6 @@
   #:use-module (gnu packages linux)
   #:use-module (gnu packages lua)
   #:use-module (gnu packages m4)
-  #:use-module (gnu packages mono)
   #:use-module (gnu packages mp3)
   #:use-module (gnu packages multiprecision)
   #:use-module (gnu packages music)
@@ -2306,58 +2305,6 @@ specific knowledge of the hardware they are targeting.")
 double-buffering.")
     (license license:gpl2+)))
 
-(define-public fna
-  (package
-    (name "fna")
-    (version "19.12.01")
-    (source
-     (origin
-       (method git-fetch)
-       (uri (git-reference
-             (url "https://github.com/FNA-XNA/FNA")
-             (commit version)))
-       (file-name (git-file-name name version))
-       (sha256
-        (base32 "1vdyi9hac24fqcs8kpj6yk36bf5rrl4dvlvdd9fc701fawcf6lrr"))))
-    (build-system gnu-build-system)
-    (arguments
-     '(#:tests? #f                      ; No tests.
-       #:phases
-       (modify-phases %standard-phases
-         (add-after 'unpack 'link-dep-src
-           (lambda* (#:key inputs #:allow-other-keys)
-             (let ((sdl2 (assoc-ref inputs "sdl2-cs-src"))
-                   (mojoshader (assoc-ref inputs "mojoshader-src"))
-                   (faudio (assoc-ref inputs "faudio-src"))
-                   (theorafile (assoc-ref inputs "theorafile-src")))
-               (symlink (string-append sdl2 "/src") "lib/SDL2-CS/src")
-               (symlink (string-append mojoshader "/csharp") "lib/MojoShader/csharp")
-               (symlink (string-append faudio "/csharp") "lib/FAudio/csharp")
-               (symlink (string-append theorafile "/csharp") "lib/Theorafile/csharp"))))
-         (delete 'configure)
-         (replace 'build
-           (lambda _
-             (invoke "make" "release")))
-         (replace 'install
-           (lambda* (#:key outputs #:allow-other-keys)
-             (let ((out (assoc-ref outputs "out")))
-               (install-file "bin/Release/FNA.dll" (string-append out "/lib"))
-               #t))))))
-    (native-inputs
-     (list mono))
-    (inputs `(("sdl2-cs-src" ,(package-source sdl2-cs))
-              ("mojoshader-src" ,(package-source mojoshader-cs))
-              ("faudio-src" ,(package-source faudio))
-              ("theorafile-src" ,(package-source theorafile))))
-    (home-page "https://fna-xna.github.io/")
-    (synopsis "Accuracy-focused XNA4 reimplementation")
-    (description "FNA is a Microsoft XNA Game Studio 4.0 reimplementation that
-focuses solely on developing a fully accurate XNA4 runtime for the desktop.")
-    (license (list license:ms-pl        ; FNA
-                   license:lgpl2.1      ; LzxDecoder.cs
-                   ;; Mono.Xna:
-                   license:expat))))
-
 (define-public libccd
   (package
     (name "libccd")