storage: support column compression flag
Merge pull request #32 from naoa/support-column-compression-flag

storage: support column compression flag

Patch by Naoya Murakami. Thanks!!!
Add missing length check

It may cause SEGV.
Use MySQL warning instead of Groonga log for invalid column flags

Because it is difficult to find specified flag is invalid.

Tests are disabled for now.

TODO:

  * Add system variable to show whether libgroonga supports zlib/lz4 or not.
  * Skip the current tests when libgroonga doesn't support zlib/lz4.
  * Add tests for libgroonga doesn't support zlib/lz4 cases. In the
    cases, Mroonga should reports a warning.
Use more meaningful name and description
Fold a long line
Remove needless "." at the end of error message
Use MySQL warning instead of Groonga log for invalid column flags
debian: support security updated MySQL
doc: remove garbage
doc: fix format
cmake: use "mroonga" instead of "ha_mroonga" for plugin name

GitHub: fix #30
Use CXX flags

Because we use C++ for all files.
Fix wrong extern declaration

It should in 'extern "C" {...}' scope.

It may fix #28 on GitHub.