Some debug info and comments added


include/pagecache.h:
  postmerge fix
mysys/mf_pagecache.c:
  Postmerge fix (including changing type of LSN)
  Additional DBUG_ASSERTs added
  Comment about pinning mechanism added
storage/maria/ma_control_file.c:
  Used the same LSN storing procedure everywhere
  Postmerge fix (including changing type of LSN)
storage/maria/ma_control_file.h:
  Postmerge fix (including changing type of LSN)
storage/maria/ma_loghandler.c:
  Postmerge fix (including changing type of LSN)
storage/maria/ma_loghandler.h:
  Postmerge fix (including changing type of LSN)
storage/maria/ma_loghandler_lsn.h:
  Postmerge fix (including changing type of LSN)
storage/maria/unittest/Makefile.am:
  Postmerge fix
storage/maria/unittest/ma_control_file-t.c:
  Postmerge fix (including changing type of LSN)
storage/maria/unittest/ma_test_loghandler-t.c:
  Postmerge fix (including changing type of LSN)
storage/maria/unittest/ma_test_loghandler_multigroup-t.c:
  Postmerge fix (including changing type of LSN)
storage/maria/unittest/ma_test_loghandler_multithread-t.c:
  Postmerge fix (including changing type of LSN)
storage/maria/unittest/ma_test_loghandler_pagecache-t.c:
  Postmerge fix (including changing type of LSN)
storage/maria/unittest/mf_pagecache_consist.c:
  Postmerge fix (including changing type of LSN)
storage/maria/unittest/mf_pagecache_single.c:
  Postmerge fix (including changing type of LSN)