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.

 ## Process this file with automake to produce Makefile.in

 pkgconfigdir = $(libdir)/pkgconfig

 pkgconfig_DATA = razor.pc

 bashcompletiondir = ${SYSCONFDIR}/bash_completion.d

 dist_bashcompletion_DATA = razor.sh

 clean-local :

 	rm -f *~