Extension of pcilib register API

[Suren A. Chilingaryan]

We need some extension of pcitool API to provide more information about registers:

• ticket #67 requires min/max fields in the pcilib_register_description_t: There is already a default value field. However, it would be extremely helpful to have minimum and maximum possible values (this is possible with GParamSpec) for each register (AFAICT the CMOSIS spec provides them).
• ticket #77 requires enums describing device statuses.

As matter of fact we probably should introduce two types of registers (more?): range and enums. First should include min & max values (function transcoding the value in standard units?), second the string names of all possible values.
Also we may provide a get_status function for event engine. Cons: doing it in scripts is more flexible. Pros: from application it is easier to call library function than external script.

[Suren A. Chilingaryan]

Since r320 the public-API functions pcilib_get_register_info and pcilib_get_register_list provide information on ranges and names if specified in XML.

The status can be provided using new property API and programmed using Python scripts (currently only one-liners are supported, but will be extended in future).