Fix missing initializer for field warnings

This is basically a false-positive by GCC since static variables are
unambiguously zeroed-out per the language standard, but the workaround
is simple enough.

ctags/main/xtag.c

@@ -27,18 +27,18 @@ static bool isPseudoTagsEnabled (xtagDesc *pdesc CTAGS_ATTR_UNUSED)
 
 static xtagDesc xtagDescs [] = {
 	{ true, 'F',  "fileScope",
-	  "Include tags of file scope" },
+	  "Include tags of file scope", NULL},
 	{ false, 'f', "inputFile",
-	  "Include an entry for the base file name of every input file"},
+	  "Include an entry for the base file name of every input file", NULL},
 	{ false, 'p', "pseudo",
 	  "Include pseudo tags",
 	  isPseudoTagsEnabled},
 	{ false, 'q', "qualified",
-	  "Include an extra class-qualified tag entry for each tag"},
+	  "Include an extra class-qualified tag entry for each tag", NULL},
 	{ false, 'r', "reference",
-	  "Include reference tags"},
+	  "Include reference tags", NULL},
 	{ false, 's', "subparser",
-	  "Include tags generated by sub parsers"},
+	  "Include tags generated by sub parsers", NULL},
 };
 
 extern xtagDesc* getXtagDesc (xtagType type)