syntax-check: Improve sc_prohibit_config_h_in_headers check
syntax-check: Improve sc_prohibit_config_h_in_headers check

In its current form, the check will not only catch the intended

  #include <config.h>

but also stuff like

  #include <wireshark/config.h>
  #include "qemu_interop_config.h"
  #include <meson-config.h>

The last one is problematic, because it's used in config.h itself.
Making the pattern more strict allows us to drop the exception.

Signed-off-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>
Reviewed-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

libvirt/libvirt,zippy2/libvirt,libvirt/libvirt,olafhering/libvirt,zippy2/libvirt,libvirt/libvirt,olafhering/libvirt,libvirt/libvirt,crobinso/libvirt,jfehlig/libvirt,zippy2/libvirt,olafhering/libvirt,crobinso/libvirt,jfehlig/libvirt,jfehlig/libvirt,crobinso/libvirt,crobinso/libvirt,olafhering/libvirt,zippy2/libvirt,jfehlig/libvirt