Adds --without-mmal option to configure.

As documented in issue 169, the recentlay added MMAL camera support for the
Raspberry Pi does not build on the Wheezy version of Raspbian.
This option disables the autoconf generation of MMAL dependencies.

configure.ac

@@ -389,14 +389,22 @@ AM_COND_IF([FOUND_PKGCONFIG],,[AC_MSG_ERROR([Required package 'pkg-config' not f
 
 # Check for raspberry pi mmal interface
 #
-HAVE_MMAL=""
-LIBRASPBERRYPIDEVPATH="/opt/vc/include/interface/mmal"
+WITHOUT_MMAL="no"
+AC_ARG_WITH([mmal],
+AS_HELP_STRING([--without-mmal],
+               [Compile without RaspberyPi mmal camera support]),
+WITHOUT_MMAL="yes",
+WITHOUT_MMAL="no")
 
-if test -d ${LIBRASPBERRYPIDEVPATH}; then
+if test "${WITHOUT_MMAL}" = "no"; then
+  HAVE_MMAL=""
+  LIBRASPBERRYPIDEVPATH="/opt/vc/include/interface/mmal"
+
+  if test -d ${LIBRASPBERRYPIDEVPATH}; then
        HAVE_MMAL="yes"
-fi
+  fi
 
-AS_IF([test "${HAVE_MMAL}" = "yes" ], [
+  AS_IF([test "${HAVE_MMAL}" = "yes" ], [
            AC_SUBST(MMAL_CFLAGS)
            AC_SUBST(MMAL_OBJ)
            AC_SUBST(MMAL_LIBS)
@@ -404,7 +412,8 @@ AS_IF([test "${HAVE_MMAL}" = "yes" ], [
            MMAL_CFLAGS="-std=gnu99 -DHAVE_MMAL -Irasppicam -I/opt/vc/include"
            MMAL_LIBS="-L/opt/vc/lib  -lmmal_core -lmmal_util -lmmal_vc_client -lvcos -lvchostif -lvchiq_arm"
            AC_DEFINE([HAVE_MMAL], 1, [Define to 1 if we want MMAL])
-])
+  ])
+fi
 
 #
 # Check for libavcodec and libavformat from ffmpeg
@@ -1230,6 +1239,8 @@ if test "${HAVE_MMAL}" = "yes"; then
     echo " ... MMAL_CFLAGS: $MMAL_CFLAGS"
     echo " ... MMAL_OBJ: $MMAL_OBJ"
     echo " ... MMAL_LIBS: $MMAL_LIBS"
+elif test "${WITHOUT_MMAL}" = "yes"; then
+    echo "MMAL support:        disabled"
 else
     echo "MMAL support:        No"
     echo " ... libraspberrypi-dev package not installed"