storage/maria/ma_pagecache.c:
  Fixed ability to read without read lock acquiring.
storage/maria/unittest/CMakeLists.txt:
  New unit test which tests simple read and prolonged writes consistency added.
storage/maria/unittest/Makefile.am:
  New unit test which tests simple read and prolonged writes consistency added.
storage/maria/unittest/ma_pagecache_rwconsist2.c:
  New unit test which tests simple read and prolonged writes consistency added.