NSURLSession rewrite (#422)

* clang-format: Do not use tabs

* Ignore clangd cache and compile_commands

* NSBlockOperation: Fix memory leak

* NSHTTPCookie: Fix expires date parsing

* NSHTTPCookie: Release DateFormatter after use

* NSOperation: Remove all objects at end of execution

* Reimplementation of NSURLSession

* NSURLSession: Update expiration dates in test

* Update ChangeLog

* Fix trivial compiler warning caused by missing import

* Import GSDispatch.h for definition of DISPATCH_QUEUE_SERIAL

* Import common.h early to avoid header conflict

* Fix import order to avoid conflicts and ensure we have correct localisation macro

* Check for presence of dispatch_cancel

* Cancel timer using dispatch_source_cancel() if dispatch_cancel() is missing.

* NSURLSession: Replace dispatch_io with dispatch_source in unit test HTTP server

---------

Co-authored-by: hmelder <service@hugomelder.com>

Source/NSOperation.m

@@ -593,13 +593,15 @@ static NSArray	*empty = nil;
 
 - (void) main
 {
-  NSEnumerator 		*en = [[self executionBlocks] objectEnumerator];
+  NSEnumerator 		*en = [_executionBlocks objectEnumerator];
   GSBlockOperationBlock theBlock;
 
   while ((theBlock = (GSBlockOperationBlock)[en nextObject]) != NULL)
     {
       CALL_NON_NULL_BLOCK_NO_ARGS(theBlock);
     }
+
+  [_executionBlocks removeAllObjects];
 }
 @end