The AC_PROC_OBJCXX inclusion is suggested by the automake error message.
The AC_LANG_PROGRAM quoting is suggested by Diego Pettenò:
  http://www.flameeyes.eu/autotools-mythbuster/forwardporting/autoconf.html

diff -ru a/configure.ac b/configure.ac
--- a/configure.ac	2011-10-24 15:00:49.000000000 -0400
+++ b/configure.ac	2012-06-23 14:28:02.034647315 -0400
@@ -37,6 +37,7 @@
 dnl Checks for programs.
 AC_PROG_CC
 AC_PROG_CXX
+AC_PROC_OBJCXX
 AC_PROG_F77
 AC_PROG_CPP
 AC_PROG_MAKE_SET
diff -ru a/m4/boinc_check_fcgi.m4 b/m4/boinc_check_fcgi.m4
--- a/m4/boinc_check_fcgi.m4	2008-11-06 19:15:24.000000000 -0500
+++ b/m4/boinc_check_fcgi.m4	2012-06-23 14:41:02.160679931 -0400
@@ -6,7 +6,7 @@
     save_cflags="${CFLAGS}"
     CFLAGS="-I${prefix} -include fcgi_stdio.h -D_USING_FCGI_ ${CFLAGS}"
     AC_COMPILE_IFELSE(
-      AC_LANG_PROGRAM(
+      [AC_LANG_PROGRAM(
         [[
 #define CONFIG_TEST
         ]],
@@ -14,7 +14,7 @@
 fprintf(stderr,"Hello\n");
 return 0;
         ]
-      ),
+      )],
       [
         AC_MSG_RESULT(yes)
       ],
diff -ru a/m4/libcurl.m4 b/m4/libcurl.m4
--- a/m4/libcurl.m4	2009-01-13 18:06:02.000000000 -0500
+++ b/m4/libcurl.m4	2012-06-23 14:40:30.724678551 -0400
@@ -179,7 +179,7 @@
            _libcurl_save_libs=$LIBS
            LIBS="$LIBS $LIBCURL"
 
-           AC_LINK_IFELSE(AC_LANG_PROGRAM([#include <curl/curl.h>],[
+           AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <curl/curl.h>],[
 /* Try and use a few common options to force a failure if we are
    missing symbols or can't link. */
 int x;
@@ -190,7 +190,7 @@
 x=CURLOPT_ERRORBUFFER;
 x=CURLOPT_STDERR;
 x=CURLOPT_VERBOSE;
-]),libcurl_cv_lib_curl_usable=yes,libcurl_cv_lib_curl_usable=no)
+])],libcurl_cv_lib_curl_usable=yes,libcurl_cv_lib_curl_usable=no)
 
            CPPFLAGS=$_libcurl_save_cppflags
            LIBS=$_libcurl_save_libs