Added extensions_case keyword in filehighlight.syntax file.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>

misc/syntax/filehighlight.syntax

@@ -23,6 +23,7 @@ context default
     keyword = brightcyan
     keyword ; brightmagenta
     keyword whole extensions yellow
+    keyword whole extensions_case yellow
     keyword whole type yellow
     keyword DEVICE brightred
     keyword DIR brightred