Add --without-hdf flag

Prevent automagic dependencies as per:
  http://www.gentoo.org/proj/en/qa/automagic.xml

--- a/configure.in
+++ b/configure.in
@@ -49,11 +49,14 @@ LIBS="-lz -lm"
 # If mounting with shared libraries we may have to specify all possible libraries.
 # First check with simple LIBS list, if it fails, then expand the list.
 
-AC_CHECK_LIB(implode,  _implode,           ,,$LIBDIR)
-AC_CHECK_LIB(jpeg,     jpeg_CreateCompress,,,$LIBDIR)
-AC_CHECK_LIB(df,       DFopen,             ,,$LIBDIR)
-AC_CHECK_LIB(mfhdf,    SDstart,            ,,$LIBDIR)
-AC_CHECK_LIB(tsdistk,  TKopen,             ,,$LIBDIR)
+AC_ARG_WITH([hdf], AS_HELP_STRING([--without-hdf], [Build without hdf library (default: test)]))
+AS_IF([test "x$with_hdf" != "xno"], [
+    AC_CHECK_LIB(implode,  _implode,           ,,$LIBDIR)
+    AC_CHECK_LIB(jpeg,     jpeg_CreateCompress,,,$LIBDIR)
+    AC_CHECK_LIB(df,       DFopen,             ,,$LIBDIR)
+    AC_CHECK_LIB(mfhdf,    SDstart,            ,,$LIBDIR)
+    AC_CHECK_LIB(tsdistk,  TKopen,             ,,$LIBDIR)
+])
 
 # Because -letor may depend on RSL being installed, just check for
 # the library libetor.a in a couple of places.