Correct impl. of HasFlag and ResolveChannel

HasFlag was checking if any of the flags were set, not the ones
specified, and ResolveChannel was still treating the ChannelPermission
enum as before it was changed to a bitflag.

src/Discord.Net.Core/Utils/Permissions.cs

@@ -80,7 +80,7 @@ namespace Discord
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static bool HasFlag(ulong value, ulong flag) => (value & flag) != 0;
+        private static bool HasFlag(ulong value, ulong flag) => (value & flag) == flag;
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void SetFlag(ref ulong value, ulong flag) => value |= flag;
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -161,10 +161,10 @@ namespace Discord
                     else if (!GetValue(resolvedPermissions, ChannelPermission.SendMessages))
                     {
                         //No send permissions on a text channel removes all send-related permissions
-                        resolvedPermissions &= ~(1UL << (int)ChannelPermission.SendTTSMessages);
-                        resolvedPermissions &= ~(1UL << (int)ChannelPermission.MentionEveryone);
-                        resolvedPermissions &= ~(1UL << (int)ChannelPermission.EmbedLinks);
-                        resolvedPermissions &= ~(1UL << (int)ChannelPermission.AttachFiles);
+                        resolvedPermissions &= ~(ulong)ChannelPermission.SendTTSMessages;
+                        resolvedPermissions &= ~(ulong)ChannelPermission.MentionEveryone;
+                        resolvedPermissions &= ~(ulong)ChannelPermission.EmbedLinks;
+                        resolvedPermissions &= ~(ulong)ChannelPermission.AttachFiles;
                     }
                 }
                 resolvedPermissions &= mask; //Ensure we didnt get any permissions this channel doesnt support (from guildPerms, for example)
@@ -173,4 +173,4 @@ namespace Discord
             return resolvedPermissions;
         }
     }
-}
+}