Fix for USE_FRM and crashed index file


configure.in:
  Fix for MacOSX and symlinks
myisam/mi_open.c:
  Give better error message in case of of crashed index file
mysql-test/r/repair.result:
  new test case
mysql-test/r/update.result:
  new test case
mysql-test/t/repair.test:
  Added test with crashed MyISAM index header
mysql-test/t/update.test:
  Added test case from bugs system
sql/handler.cc:
  Indentation changes
sql/sql_table.cc:
  Fix for USE_FRM and crashed index file