Build system: adding -Wall when building MEX files

(cherry picked from commit e347f2ae)

mex/build/matlab/configure.ac

@@ -50,6 +50,9 @@ case ${host_os} in
     ;;
 esac
 
+CFLAGS="$CFLAGS -Wall"
+CXXFLAGS="$CXXFLAGS -Wall"
+
 AC_PROG_CC
 AC_PROG_CXX
 AC_PROG_RANLIB

mex/build/octave/configure.ac

@@ -31,6 +31,9 @@ if test "x$MKOCTFILE" != "x"; then
   CXXFLAGS=`$MKOCTFILE -p CXXFLAGS`
 fi
 
+CFLAGS="$CFLAGS -Wall"
+CXXFLAGS="$CXXFLAGS -Wall"
+
 AC_PROG_CC
 AC_PROG_CXX
 AC_PROG_RANLIB