* src/bridge.c, src/qemu_driver.c, configure.in: Try to detect
the paths of dnsmasq and brctl at compile time. If found
then compile them in, otherwise search $PATH at runtime.
* libvirt.spec.in: BR dnsmasq and bridge-utils so we have their
paths at compile time.
* acinclude.m4, configure.in: ./configure option
--disable-stack-protector.
* src/gnutls_1_0_compat.h: Compatibility with GnuTLS 1.0.
* src/bridge.c: If no bridge ioctls, give an error at runtime.