Fix dependencies in compiler/ and fix parallel compilation.

Missing dependencies:

  %.mli: %.mly
  %.mli: %.mll

The 'make depend' target did not generate the following dependendcy
when called from a fresh 'git clone' (or after a 'git clean -dxf'):

  linker.cmo: ... annot_parser.cmo ...
Merge pull request #57 from hnrgrgr/master

Fix dependencies in compiler/ and fix parallel compilation.