[autoconf] bugs 162,303,178: Fix 'present but can not be compiled' warnings

[autoconf] bugs 162,303,178: Fix 'present but can not be compiled' warnings

2007-05-09 Paul Jakma <paul.jakma@sun.com>

	* configure.ac: sys/conf.h depends on sys/param.h, at least on
	  FBSD 6.2.
	  (bug #363) Should check for in_pktinfo for IRDP

2006-05-27 Paul Jakma <paul.jakma@sun.com>

	* configure.ac: General cleanup of header and type checks, introducing
	  an internal define, QUAGGA_INCLUDES, to build up a list of
	  stuff to include so as to avoid 'present but cant be compiled'
	  warnings.
	  Misc additional checks of things missing according to autoscan.
	  Add LIBM, for bgpd's use of libm, so as to avoid burdening
	  LIBS, and all the binaries, with libm linkage.
	  Remove the bad practice of using m4 changequote(), just
	  quote the []'s in the case statements properly.
	  This should fix bugs 162, 303 and 178.
	* */*.{c,h}: Update all HAVE_* to the standard autoconf namespaced
	  HAVE_* defines. I.e. HAVE_SA_LEN -> HAVE_STRUCT_SOCKADDR_SA_LEN,
	* bgpd/Makefile.am: Add LIBM to bgpd's LDADD, for pow().