Improve error message for duplicate rules and unknown pools.

Also add more tests for invalid manifests. According to gcov, these invalid
inputs weren't tested before.
Mention pools in the discussion of ninja's toplevel declarations.
Fix murmur hash implementations to work on strict alignment
architectures like OpenBSD/mips64el and OpenBSD/hppa64.
Merge pull request #615 from mdempsky/strict-murmur

Fix murmur hash implementations to work on strict alignment architectures
Add a 'recompact' tool, which forces recompaction of the build and deps logs.

This is useful for performance comparisons between two build directories.
Introducing tool 'deps' dumping ninja deps log entries
Merge pull request #611 from nico/testparse

Improve error message for duplicate rules and unknown pools.
Merge pull request #614 from nico/pooldoc

Mention pools in the discussion of ninja's toplevel declarations.
Merge pull request #616 from nico/recompact

Add a 'recompact' tool, which forces recompaction of the build and deps ...