[ompi|opal]_setup_cxx.m4: ensure to use the C++ compiler (!)

We didn't AC_LANG_PUSH(C++) before checking to see if the compiler
supports -finline-functions, meaning that configure used the C
compiler for these checkes, not the C++ compiler.

Due to #2999, we have to fix both opal_setup_cxx.m4 and
ompi_setup_cxx.m4.

cmr=v1.8.2:reviewer=rolfv

This commit was SVN r31651.

config/ompi_setup_cxx.m4

@@ -214,11 +214,13 @@ AC_DEFUN([_OMPI_SETUP_CXX_COMPILER_BACKEND],[
         CXXFLAGS_orig="$CXXFLAGS"
         CXXFLAGS="$CXXFLAGS -finline-functions"
         add=
+        AC_LANG_PUSH(C++)
         AC_CACHE_CHECK([if $CXX supports -finline-functions],
                    [ompi_cv_cxx_finline_functions],
                    [AC_TRY_COMPILE([], [],
                                    [ompi_cv_cxx_finline_functions="yes"],
                                    [ompi_cv_cxx_finline_functions="no"])])
+        AC_LANG_POP(C++)
         if test "$ompi_cv_cxx_finline_functions" = "yes" ; then
             add=" -finline-functions"
         fi

config/opal_setup_cxx.m4

@@ -152,11 +152,13 @@ AC_DEFUN([_OPAL_SETUP_CXX_COMPILER_BACKEND],[
         CXXFLAGS_orig="$CXXFLAGS"
         CXXFLAGS="$CXXFLAGS -finline-functions"
         add=
+        AC_LANG_PUSH(C++)
         AC_CACHE_CHECK([if $CXX supports -finline-functions],
                    [opal_cv_cxx_finline_functions],
                    [AC_TRY_COMPILE([], [],
                                    [opal_cv_cxx_finline_functions="yes"],
                                    [opal_cv_cxx_finline_functions="no"])])
+        AC_LANG_POP(C++)
         if test "$opal_cv_cxx_finline_functions" = "yes" ; then
             add=" -finline-functions"
         fi