Patch from Frederic Bouvier:

I am trying to compile tabbed_values.cxx and found that it requires
assert.h to compile with MSVC (on Linux, it must be included indirectly).
There is a patch below

simgear/misc/tabbed_values.cxx

@@ -1,5 +1,7 @@
 #include "tabbed_values.hxx"
 
+#include "assert.h"
+
 SGTabbedValues::SGTabbedValues(const char *line) :
 	_line(line)
 {