convert the NULL sentinel to RAZOR_DETAIL_LAST

Get rid of razor_set_get_package().

This was always a silly little helper function, not general enough for
real world applications. Use an iterator to search through the set to
find the package of interest.

Tweak razor search a bit: casefold, print summary, search rawhide instead.

the vararg list must be terminated with zero else 64bit machines may crash

On 64 bit systems, the integer 0 is 32 bits and the pointer 0 is 64 bits.
The upper 32 bits will not be cleared and the loop will never terminate.
Also add the RAZOR_SENTINEL __attribute__ ((__sentinel__(0))) on GCC4
so we catch where we get this wrong automatically.

This also fixes the new search functionality from James which was missed
in the merge.

trivial: razor_property_iterator_create() can have package NULL and be valid

convert razor_package_get_details() and razor_package_iterator_next() to varargs

The functions for getting package details about a package were limited to a few
things, when in the future we will want to support much more about a package.
The iterator was also limited to name,version,arch when most of the time we
didn't need all this data.

protect all exported functions by checking the input parameters for NULL input

add missing licencing information at the top of each source file

The licence text is needed when razor is packaged for Debian. :-)

Remove a couple of done TODO items.

Merge commit 'fdo/master'