Add optimizer option '-' to read from stdin

This allows a user to run the optimizer as part of a pipeline., e.g.:

  vobla foo.vobla | optimizer -

Change-Id: I8074e12f02f2989361767e6ed6395b2aa7617cc2
Update README.txt with links to dependencies.

Change-Id: I72878977b6fa5aa8123a489723071513c5fc0cbd
Support hexadecimal integer constants.

Change-Id: I8bc360e1dc7fb42f75cfdba48866ca2653dcf882
Add initial version of pencil.h

Change-Id: Ieff346fe6a02ba29cabfb9bb30682a4f9e683f4b
Let testsuite use pencil.h

Change-Id: I35a36e7cc0bf5dc44d10f2d2b6cdc18307e808ab
Check lvalue type for const modifier.

Change-Id: I2a8f7bc4dffaf0ce1d52e5f22069809f37baad78
Allow direct struct subscription for function calls.

For functions returning structs the following is
legal now:
foo().s;

Change-Id: Ic84733f75c60e2e312df059b6d3fe1d3f86dcaf1
Fix struct flattening in the return operation.

Change-Id: I1638a400c0d24e20a4e8f305f072dce50b316369