patch 9.0.1425: "wat" and "wast" files are one filetype

Problem:    "wat" and "wast" files are one filetype.
Solution:   Add a separate filetype for "wat" files. (Amaan Qureshi,
            closes #12165)

runtime/filetype.vim

@@ -2343,7 +2343,8 @@ au BufNewFile,BufRead *.vroom			setf vroom
 au BufNewFile,BufRead *.vue			setf vue
 
 " WebAssembly
-au BufNewFile,BufRead *.wast,*.wat		setf wast
+au BufNewFile,BufRead *.wat			setf wat
+au BufNewFile,BufRead *.wast		setf wast
 
 " WebAssembly Interface Type (WIT)
 au BufNewFile,BufRead *.wit			setf wit

src/testdir/test_filetype.vim

@@ -657,7 +657,8 @@ let s:filename_checks = {
     \ 'vrml': ['file.wrl'],
     \ 'vroom': ['file.vroom'],
     \ 'vue': ['file.vue'],
-    \ 'wast': ['file.wast', 'file.wat'],
+    \ 'wat': ['file.wat'],
+    \ 'wast': ['file.wast'],
     \ 'wdl': ['file.wdl'],
     \ 'webmacro': ['file.wm'],
     \ 'wget': ['.wgetrc', 'wgetrc'],

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1425,
 /**/
     1424,
 /**/