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.

 prefix=@prefix@

 exec_prefix=@exec_prefix@

 libdir=@libdir@

 includedir=@includedir@

 Name: razor

 Description: library for depsolving, installing and removing packages

 Version: @VERSION@

 Requires: libcurl

 Libs: -L${libdir} -lexpat -lz -lrazor

 Cflags: -I${includedir}/razor