patch 8.2.3814: .csx files and .sln files are not recognized

Problem:    .csx files and .sln files are not recognized.
Solution:   Add filetype patterns. (Doug Kearns)

src/testdir/test_filetype.vim

@@ -117,7 +117,7 @@ let s:filename_checks = {
     \ 'cpp': ['file.cxx', 'file.c++', 'file.hh', 'file.hxx', 'file.hpp', 'file.ipp', 'file.moc', 'file.tcc', 'file.inl', 'file.tlh'],
     \ 'crm': ['file.crm'],
     \ 'crontab': ['crontab', 'crontab.file', '/etc/cron.d/file', 'any/etc/cron.d/file'],
-    \ 'cs': ['file.cs'],
+    \ 'cs': ['file.cs', 'file.csx'],
     \ 'csc': ['file.csc'],
     \ 'csdl': ['file.csdl'],
     \ 'csp': ['file.csp', 'file.fdr'],
@@ -458,6 +458,7 @@ let s:filename_checks = {
     \ 'skill': ['file.il', 'file.ils', 'file.cdf'],
     \ 'slang': ['file.sl'],
     \ 'slice': ['file.ice'],
+    \ 'solution': ['file.sln'],
     \ 'slpconf': ['/etc/slp.conf', 'any/etc/slp.conf'],
     \ 'slpreg': ['/etc/slp.reg', 'any/etc/slp.reg'],
     \ 'slpspi': ['/etc/slp.spi', 'any/etc/slp.spi'],

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3814,
 /**/
     3813,
 /**/