mesa/es: Generate code for special functions.

mesa/es: Generate code for special functions.

es_generator.py did not generate code for special functions.  They were
supposed to be defined elsewhere.  But as a result, parameter checking
was also skipped.  This commit changes the way special functions are
called so that parameter checking is always performed.

When there is nothing to check, the check functions becomes macros
expanding to the real functions, as an optimization.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>