python hal module broken badly in master branch

[jepler]

Original report is of code that works in 2.7.4 but not in ja12.

I reproduced the same error message in master branch running interactively:

>>> import hal
>>> c = hal.component("bob")
>>> c.newparam("g", hal.HAL_FLOAT, hal.HAL_RW)
>>> c['g'] = 1.0
SystemError: null argument to internal routine

I strongly suspect this was introduced by 2b6c8ad ("halmodule: factor out to/from python functions") but I didn't test this theory yet.