C#: Correctly parse enums with a base type specifier

See CSharp Language Specification 14.1.

tagmanager/ctags/c.c

@@ -2637,7 +2637,8 @@ static void processColon (statementInfo *const st)
 			else if (c == ';')
 				setToken (st, TOKEN_SEMICOLON);
 		}
-		else if (isLanguage (Lang_cpp) && st->declaration == DECL_ENUM)
+		else if ((isLanguage (Lang_cpp) || isLanguage (Lang_csharp)) &&
+				 st->declaration == DECL_ENUM)
 		{
 			/* skip enum's base type */
 			c = skipToOneOf ("{;");

tests/ctags/bug1515910.cs.tags

@@ -1,9 +1,9 @@
 # format=tagmanager
 CÌ1Ö0
+Enum1Ì2Ö0
 MyGenericClass1Ì1Ö0
-Value1Ì4ÎbyteÖ0
-ValuesÌ4ÎbyteÖ0
-byteÌ2Ö0
+Value1Ì4ÎEnum1Ö0
+ValuesÌ4ÎEnum1Ö0
 int1Ì8ÎCÖ0Ïint
 str1Ì8ÎCÖ0
 str2Ì8ÎCÖ0