Defer grammar checker thread creation until use.

Avoid this thread being started and stranded in the forkit.

Change-Id: Ia79cdac729a85960c2b5a83af265d67af07b74aa
Reviewed-on: https://gerrit.libreoffice.org/52860Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>

linguistic/source/gciterator.cxx

@@ -241,7 +241,7 @@ GrammarCheckingIterator::GrammarCheckingIterator() :
     m_aEventListeners( MyMutex::get() ),
     m_aNotifyListeners( MyMutex::get() )
 {
-    m_thread = osl_createThread( lcl_workerfunc, this );
+    m_thread = nullptr;
 }
 
 
@@ -321,6 +321,8 @@ void GrammarCheckingIterator::AddEntry(
 
         // add new entry to the end of this queue
         ::osl::Guard< ::osl::Mutex > aGuard( MyMutex::get() );
+        if (!m_thread)
+            m_thread = osl_createThread( lcl_workerfunc, this );
         m_aFPEntriesQueue.push_back( aNewFPEntry );
 
         // wake up the thread in order to do grammar checking