Added specs for rb_obj_instance_variables
Add rb_obj_instance_variables to the C-API
Fixes #2183
Merge pull request #2184 from Groogy/master

Added rb_obj_instance_variables to the C-API
Add GC guards around open() because there are cases where it can block

Caught during a CI run on Linux. open() can block for example when used
with pipes. Also make sure to handle any errors that might need to be
thrown. Using strdup here is safe, because we already ensure that the
string is a safe C null terminated string.
Make the build ruby error more helpful
Remove mailbox.rb from lib/

This file supported the actor implementation that was removed in
79bd4c3021 and should have been removed with it.
Merge pull request #2188 from jstorimer/master

Remove mailbox.rb from lib/
Fixed Process.getrlimit specs.
Fixed Process.setrlimit specs.
Fixed coercing arguments for Process.[gs]etrlimit on 1.9.
Added RLIMIT constants defined on Linux.
Added missing generated website file. [ci skip]
Use native_int not other types for Tuple sizes
Use native_int instead of size_t for Array
Use native_int for Array methods
Another case of native_int for Array
I'm getting tired of this...
Fix signedness issues in VM tests
Fix
Remove tags