my_sopen() on win32 which allows to use FILE_SHARE_DELETE flag to 
allow deleting opened files. my_sopen() implementation is added to
support this functionality.


include/my_global.h:
  Fixes bug #13377. Added number of constants for share delete file
  open option.
include/my_sys.h:
  Fixes bug #13377. Added my_sopen function.
mysys/my_create.c:
  Fixes bug #13377. my_create() function changed to use my_sopen() and which allows
  to use FILE_SHARE_DELETE flag on win32, which helps in deleting opened files.
mysys/my_open.c:
  Fixes bug #13377. my_open() function changed to use my_sopen() on win32
  which allows to use FILE_SHARE_DELETE flag to allow deleting opened files.
sql/log.cc:
  Fixes bug #13377. Additional patch - remove reference counting for
  opened binlog files, introduced in initial patch of #13377.
sql/sql_class.h:
  Fixes bug #13377. Additional patch - remove reference counting for
  opened binlog files, introduced in initial patch of #13377.
sql/sql_repl.cc:
  Fixes bug #13377. Additional patch - remove reference counting for
  opened binlog files, introduced in initial patch of #13377.