ARCHIVE table
ARCHIVE table was truncated by REPAIR TABLE ... USE_FRM statement.
The table handler returned its file name extensions in a wrong order.
REPAIR TABLE believed it has to use the meta file to create a new table
from it.

With the fixed order, REPAIR TABLE does now use the data file to create
a new table. So REPAIR TABLE ... USE_FRM works well with ARCHIVE engine
now.

This issue affects 5.0 only, since in 5.1 ARCHIVE engine stores meta
information and data in the same file.


mysql-test/r/archive.result:
  A test case for bug#26138.
mysql-test/t/archive.test:
  A test case for bug#26138.
sql/examples/ha_example.cc:
  Added a comment.
sql/ha_archive.cc:
  First element of engine file name extentions array should be meta/index
  file extention. Second element - data file extention. This is true
  for engines that have separate meta/index file and data file.
  
  Reoder ha_archive_exts elements to meet described above requirement.
sql/handler.h:
  Added a comment.
sql/sql_table.cc:
  Added a comment.