fixing bug in thread_cancellation class

when destroying a thread_cancellation object on a thread which was requested
to be cancelled, the status was kept forever in the preborn list, which purpose
is not for that but to record cancellation for thread which no thread_cancellation
object was yet run.

just deleting thread_cancellation reference from the info list is better, the
cancellation information for that tid will be forgotten once all thread_cancellation
object for that thread will be deleted.

src/build/ChangeLog

@@ -12,7 +12,9 @@ from 2.7.15 to 2.7.16
   more than the half of kept entries...
 - adding kdf support for repairing operation instead of using the values of the
   archive/backup under reparation.
-
+- fixing bug in thread_cancellation class that led a cancelled thread kept
+  being recorded as cancelled forever, leading libdar to abort immediately when
+  run in a new thread having the the same tid.
 
 from 2.7.14 to 2.7.15
 - updating libdar about CURLINFO_CONTENT_LENGTH_DOWNLOAD symbol which is

src/libdar/thread_cancellation.cpp

@@ -81,7 +81,7 @@ namespace libdar
 		status.cancellation = false;
 		status.flag = 0;
 	    }
-	    else // pending cancellation for that thread
+	    else // pending cancellation information for that thread
 	    {
 		status = *it;
 		preborn.erase(it);
@@ -118,11 +118,7 @@ namespace libdar
 	    if(*ptr == nullptr)
 		bug = true;
 	    else
-	    {
-		if((*ptr)->status.cancellation) // cancellation for that thread
-		    preborn.push_back((*ptr)->status);
 		info.erase(ptr);
-	    }
 	CRITICAL_END;
 
 	if(bug)