Thanks to Martin Friebe for finding and submitting a fix for this bug!
  
  A table with maximum number of key segments and maximum length key name
  would have a corrupted .frm file, due to an incorrect calculation of the
  complete key length.  Now the key length is computed correctly (I hope) :-)
  
  MyISAM would reject a table with the maximum number of keys and the maximum
  number of key segments in all keys.  It would allow one less than this total
  maximum.  Now MyISAM accepts a table defined with the maximum.  (This is a
  very minor issue.)


myisam/mi_open.c:
  Bug #26642: change >= to > in a comparison (i.e., error 
  only if key_parts_in_table really is greater than 
  MAX_KEY * MAX_KEY_SEG)
mysql-test/r/create.result:
  Bug #26642: test case
mysql-test/t/create.test:
  Bug #26642: test case
sql/table.cc:
  Bug #26642: In create_frm(), fix formula for key_length; 
  it was too small by (keys * 2) bytes