* CC: remove the task pool queue, it was used for priority header file parsing, but we now use recursive paring of the header files instead.

Before the change, we have such logics to parse the files:
CodeCompletion receive Workspace changed (mostly because project loaded finishes)
->NativeParser::CreateParser for the active project
  ->new Parser
  ->DoFullParsing
    ->Fill Parser's macro definition(from compiler and from project setting)
    ->Fill Parser's file list need to parse, kick the batch timer

Parser receive batch timer event
->new ParserThreadedTask (this task will executed in thread pool)
->send Parse Start Event!

ParserThreadedTask is executed
->parse the macro definition
->new ParserThread for each file in file list
->put ParserThread in task pool queue

Thread pool finish running tasks:
->do one of below
  *CASE1: if task pool queue is not empty, copy to thread pool, run
  *CASE2: if file list is not empty, kick the batch timer
  *CASE3: if macro definition is not empty, kick the batch timer
  *CASE4: non of the above cases, send Parse Finish Event!

In this commit, we don't need to copy the ParserThread to task pool queue, and later to thread pool, we can directly put the ParserThread to the thread pool.

git-svn-id: https://svn.code.sf.net/p/codeblocks/code/trunk@9883 2a5c6006-c6dd-42ca-98ab-0921f2732cef
- CC: many comments added and some wrong comments were fixed.

git-svn-id: https://svn.code.sf.net/p/codeblocks/code/trunk@9884 2a5c6006-c6dd-42ca-98ab-0921f2732cef