[Open-scap] [PATCHes] OpenSCAP symbol visibility + cleanups

[Lukas Kuklinek]

> - Many xccdf_{benchmark,check,fixtext,group,item,profile,rule,value}_get_
> functions are automatically generated, but they are missing from header
>  files. I think the prototypes should be added in this case.

There is a structure called xccdf_item_base, which is common for all
the groups, profiles, rules, etc. Not all its members make sense in all cases,
therfore they shall not be availible in the public API. It is also possible
I have forgotten to export some functions. I'm going to hide / delete 
unnecessary symbols as soon as Mirek's patch gets applied.

Have a nice day

Lukas