Fix format not a string literal
Use fileutils rather than ftools for Ruby 1.9
Use RbConfig rather than Config for Ruby 1.9
Use RUBY_VERSION rather than VERSION for Ruby 1.9
Add magic comment for Ruby 1.9
Use macros for Ruby 1.9
Set rubylibdir to MHC_LIBDIR for Ruby 1.9

For Ruby 1.9.3, the sub directory "1.9" should be "1.9.1" which is
the library compatibility version.
Workaround with force_encoding for Ruby 1.9
Merge pull request #2 from tats/bug/format-string

Fix format not a string literal
Merge pull request #3 from tats/feature/ruby19

Support Ruby 1.9
Use StringValuePtr rather than obsolete STR2CSTR for Ruby 1.9
Merge pull request #4 from tats/bug/str2cstr

Use StringValuePtr rather than obsolete STR2CSTR for Ruby 1.9