The parser was not using the correct fully-qualified-name
production for DROP FUNCTION.
Fixed by copying the production from DROP PROCEDURE.
Tested in the windows specific suite to make sure it's 
tested on a case-insensitive file system.

mysql-test/r/windows.result:
  Bug #33813: test case
mysql-test/t/windows.test:
  Bug #33813: test case
sql/sql_yacc.yy:
  Bug #33813: use the correct production for the name in
  DROP PROCEDURE