Set default variable to allow both --enable-x/--disable-x and
 --with-x/--without-x to work as expected.

bicatali@gentoo.org 08/2012

--- configure.ac.orig	2012-08-20 17:46:41.000000000 +0100
+++ configure.ac	2012-08-20 17:56:23.000000000 +0100
@@ -37,7 +37,7 @@
 # Option to disable Fortran (benchmarks will not compile)
 AC_MSG_CHECKING([whether to enable Fortran compilation for benchmark codes])
 AC_ARG_ENABLE(fortran,
-  AS_HELP_STRING([--enable-fortran],[Enable Fortran compilation]),,[
+  AS_HELP_STRING([--enable-fortran],[Enable Fortran compilation]),enable_fortran=$enableval,[
   enable_fortran="yes"])
 AC_MSG_RESULT([$enable_fortran])
 AM_CONDITIONAL(FORTRAN_ENABLED, [test $enable_fortran = yes])
@@ -96,7 +96,7 @@
 # Option to enable thread-safety (requires thread support or OpenMP)
 AC_MSG_CHECKING([whether to enable Blitz thread-safety features])
 AC_ARG_ENABLE(threadsafe,
-  AS_HELP_STRING([--enable-threadsafe],[Enable thread-safety features]),,[
+  AS_HELP_STRING([--enable-threadsafe],[Enable thread-safety features]),enable_threadsafe=$enableval,[
   enable_threadsafe="no"])
 AC_MSG_RESULT([$enable_threadsafe])
 if test "$enable_threadsafe" = yes; then
@@ -106,17 +106,22 @@
 AC_MSG_CHECKING([if we are using Intel Threading Building Blocks])
 AC_ARG_WITH([tbb],
   AS_HELP_STRING([--with-tbb],[Use Intel Threading Building Blocks atomic types]),
-    [
+    [if test x$withval != xno; then
     AC_MSG_RESULT([yes])
     AC_CHECK_HEADERS([tbb/atomic.h],,AC_MSG_ERROR([tbb/atomic.h not found]))
     AC_DEFINE([THREADSAFE_USE_TBB],[1],[Use TBB atomic types])
+    else
+    AC_MSG_RESULT([no])
+    fi
     ],AC_MSG_RESULT([no]))
 
 AC_MSG_CHECKING([for SIMD instruction width])
 AC_ARG_ENABLE([simd-width],
   AS_HELP_STRING([--enable-simd-width=n],[Facilitate compiler vectorization optimizations for SIMD instruction width of n bytes.]),
-  [ AC_ALIGNMENT_DIRECTIVE
-   AC_DEFINE([USE_ALIGNMENT_PRAGMAS],[1],[Specifies whether compiler alignment pragmas should be used]) ],
+  [if test x$enableval != xno; then
+   AC_ALIGNMENT_DIRECTIVE
+   AC_DEFINE([USE_ALIGNMENT_PRAGMAS],[1],[Specifies whether compiler alignment pragmas should be used])
+   fi ],
   [enable_simd_width=no]
   )
 AC_MSG_RESULT([$enable_simd_width])
@@ -130,12 +135,15 @@
 AC_MSG_CHECKING([whether to pad array lengths to SIMD instruction width])
 AC_ARG_ENABLE([array-length-padding],
   AS_HELP_STRING([--enable-array-length-padding],[Sets the default array padding policy to pad all lowest-rank lengths to nearest larger SIMD width. Caution: This means that arrays will in general be non-contiguous.]),
-  [
+  [if test x$enableval != xno; then
   AC_MSG_RESULT([yes])
   if test "$enable_simd_width" == [1] ; then
      AC_MSG_WARN([This option is useless without a SIMD width >1.])
   fi
   AC_DEFINE([PAD_ARRAYS],1,[Pad array lengths to SIMD width.])
+  else 
+  AC_MSG_RESULT([no])
+  fi
   ],AC_MSG_RESULT([no]))
 
 AC_MSG_CHECKING([whether to enable Blitz 64-bit dimensions])
@@ -147,10 +155,14 @@
 AC_MSG_CHECKING([whether to enable serialization support])
 AC_ARG_ENABLE([serialization],
 	AS_HELP_STRING([--enable-serialization],[Enable serialization support using Boost::Serialization]), [
+	if test x$enableval != xno; then
 	AC_MSG_RESULT([yes])
 	AX_BOOST_BASE([1.40.0])						       
 	AX_BOOST_SERIALIZATION
 	AC_CHECK_HEADERS([boost/mpi.hpp])
+	else
+	AC_MSG_RESULT([no])
+	fi
 	 ], AC_MSG_RESULT([no]))
   
 # check for PAPI library
diff -Nur m4.orig/ac_prog_doxygen.m4 m4/ac_prog_doxygen.m4
--- m4.orig/ac_prog_doxygen.m4	2012-08-20 18:03:12.000000000 +0100
+++ m4/ac_prog_doxygen.m4	2012-08-20 18:00:46.000000000 +0100
@@ -3,16 +3,16 @@
 AC_DEFUN([AC_PROG_DOXYGEN],
 [
 AC_ARG_ENABLE(doxygen,
-AS_HELP_STRING([--enable-doxygen],[enable documentation generation with doxygen (no)]),[],[enable_doxygen=no])
+AS_HELP_STRING([--enable-doxygen],[enable documentation generation with doxygen (no)]),[enable_doxygen=$enableval],[enable_doxygen=no])
 
 AC_ARG_ENABLE(dot,
-AS_HELP_STRING([--enable-dot],[use 'dot' to generate graphs in doxygen (no)]),[],[enable_dot=no])              
+AS_HELP_STRING([--enable-dot],[use 'dot' to generate graphs in doxygen (no)]),[enable_dot=$enableval],[enable_dot=no])              
 AC_ARG_ENABLE(html-docs,
 AS_HELP_STRING([--enable-html-docs],[enable HTML generation with doxygen (no)]),
-[],[ enable_html_docs=no])              
+[enable_html_docs=$enableval],[ enable_html_docs=no])              
 AC_ARG_ENABLE(latex-docs,
 AS_HELP_STRING([--enable-latex-docs],
-[enable LaTeX documentation generation with doxygen (no)]),[],[enable_latex_docs=no])              
+[enable LaTeX documentation generation with doxygen (no)]),[enable_latex_docs=$enableval],[enable_latex_docs=no])              
 
 if test "x$enable_doxygen" = xno; then
  enable_doc=no