fix shell string compare

[[Imported from SVN: r5117]]

m4/alugrid.m4

@@ -16,7 +16,7 @@ ac_save_LIBS="$LIBS"
 ## do nothing if no --with-alugrid was supplied
 if test x$with_alugrid != x && test x$with_alugrid != xno ; then
 
-  if test x$with_alugrid == xyes ; then
+  if test x$with_alugrid = xyes ; then
     AC_MSG_ERROR([You have to provide a directory --with-alugrid=PATH])
   fi
 

m4/dune.m4

@@ -143,7 +143,7 @@ AC_DEFUN([DUNE_CHECK_MODULES],[
     if test "x$enable_dunelibcheck" != "xyes"; then
       AC_MSG_WARN([library check for _dune_name is disabled. DANGEROUS!])
     fi
-    if test x$HAVE_[]_DUNE_MODULE != x -a x$enable_dunelibcheck == "xyes"; then
+    if test x$HAVE_[]_DUNE_MODULE != x -a x$enable_dunelibcheck = "xyes"; then
 
       # save current LDFLAGS
       ac_save_LDFLAGS="$LDFLAGS"

m4/dune_exprtmpl.m4

@@ -2,10 +2,10 @@ AC_DEFUN([DUNE_EXPRTMPL],[
   # enable experimental features
   AC_ARG_ENABLE(expressiontemplates,
    AC_HELP_STRING([--enable-exmpressiontemplates],[enable experimental expressiontemplates in dune]))
-  if test x$enable_expressiontemplates == xyes; then
+  if test x$enable_expressiontemplates = xyes; then
     AC_DEFINE([DUNE_EXPRESSIONTEMPLATES], [1], 
       [Define to 1 if the experimental expression templates should be used])
   fi
   AM_CONDITIONAL([EXPRESSIONTEMPLATES],
-    [test x$enable_expressiontemplates == xyes])
+    [test x$enable_expressiontemplates = xyes])
 ])
\ No newline at end of file

m4/dune_mpi.m4

@@ -85,7 +85,7 @@ AC_DEFUN([DUNE_MPI],[
   with_mpi="no"
 
   ## do nothing if --disable-parallel is used
-  if test x$with_parallel == xyes ; then
+  if test x$with_parallel = xyes ; then
   
     ACX_MPI([
       MPICOMP="$MPICC"