[PATCH] ifplugd: configure: don't check for C++ compiler

The configure script was checking for a C++ compiler (and erroring out
if not found), even though it isn't used for anything.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
diff -urpN ifplugd-0.28/configure.ac ifplugd-0.28.new/configure.ac
--- ifplugd-0.28/configure.ac	2005-06-04 21:21:51.000000000 +0200
+++ ifplugd-0.28.new/configure.ac	2008-12-13 20:31:13.000000000 +0100
@@ -33,7 +33,6 @@ if type -p stow > /dev/null && test -d /
 fi
 
 # Checks for programs.
-AC_PROG_CXX
 AC_PROG_CC
 AC_PROG_CPP
 AC_PROG_INSTALL