Fix parallel build in top-level Makefile

[electrodude]

The first commit fixes the conflict over pandoc.yml that would occur when attempting a parallel build. The second corrects some explicit recursive invocations of make with the correct $(MAKE), as explained in the manual.

@drwonky's #72 has a comment about how parallel build didn't work; this should fix that, at which point the SPEC file can be updated to use parallel build.

[electrodude]

Not quite finished yet; it sometimes fails while compiling PropLoader.