Update CONFIGURE_ARGS for how we pass CONFIGURE_TARGET to configure script.

Specifically, newer autoconf (> 2.13) has different semantic of the
configure target. In short, one should use --build=CONFIGURE_TARGET
instead of CONFIGURE_TARGET directly. Otherwise, you will get a warning
and the old semantic may be removed in later autoconf releases.

To workaround this issue, many ports hack the CONFIGURE_TARGET variable
so that it contains the ``--build='' prefix.

To solve this issue, under the fact that some ports still have
configure script generated by the old autoconf, we use runtime detection
in the do-configure target so that the proper argument can be used.

Changes to Mk/*:
 - Add runtime detection magic in bsd.port.mk
 - Remove CONFIGURE_TARGET hack in various bsd.*.mk
 - USE_GNOME=gnometarget is now an no-op

Changes to individual ports, other than removing the CONFIGURE_TARGET hack:

= pkg-plist changed (due to the ugly CONFIGURE_TARGET prefix in * executables)
  - comms/gnuradio
  - science/abinit
  - science/elmer-fem
  - science/elmer-matc
  - science/elmer-meshgen2d
  - science/elmerfront
  - science/elmerpost

= use x86_64 as ARCH
  - devel/g-wrap

= other changes
  - print/magicfilter
    GNU_CONFIGURE -> HAS_CONFIGURE since it's not generated by autoconf

Total # of ports modified:  1,027
Total # of ports affected: ~7,000 (set GNU_CONFIGURE to yes)

PR:		126524 (obsoletes 52917)
Submitted by:	rafan
Tested on:	two pointyhat 7-amd64 exp runs (by pav)
Approved by:	portmgr (pav)

1 files changed, 0 insertions, 1 deletions

diff --git a/polish/ekg2/Makefile b/polish/ekg2/Makefile
index 37a3b100e5a5..118d43e2ced7 100644
--- a/polish/ekg2/Makefile
+++ b/polish/ekg2/Makefile
@@ -22,7 +22,6 @@ GNU_CONFIGURE=	yes
 USE_GNOME=	gnomehack pkgconfig
 USE_GETTEXT=	yes
 
-CONFIGURE_TARGET=	--build=${MACHINE_ARCH}-portbld-freebsd${OSREL}
 CONFIGURE_ARGS+=	--enable-shared \
 			--disable-static \
 			--enable-dynamic \