The changelog? Perhaps the _two_ listed fixed issues (ffi build failure, Symbol GC memory leak) were just the most important ones according to the maintainer.
Fix dependencies to make bigdecimal installable by rubygems
some updates to rb_hash_delete
"restrict searching case-insensitive name from the filesystem to only last part, for the performance"
file.c (rb_file_expand_path_internal): drop characters ignored by filesystem on Mac OS X.
A GC fix on Solaris
" DNS is case-insensitive, so the comparison should be case-insensitive as well"
Some other OS specific fixes
Misc