Relative include paths are not handled correctly

[minexew]

Example 1:

main.js:

pp.run(contentsOf('main.c'), 'main.c')

main.c:

#include "subdir/a.h"

subdir/a.h:

#include "b.h"  <---- attempts to access incorrect path;
                      include_func doesn't have enough context to resolve this on its own either

subdir/b.h:

(empty)

Example 2:

main.js:

pp.run(contentsOf('subdir/main.c'), 'subdir/main.c')

subdir/main.c:

#include "a.h"  <---- attempts to access incorrect path;
                      include_func doesn't have enough context to resolve this on its own either

subdir/a.h:

(empty)