Add spec for Process.spawn

When user execute method with :pgroup => true Rubinius tried to use '<'
method on TrueClass object. It will throw an exception NoMethotError.

Process.spawn executed with :pgroup => Symbol should raise TypeError
Change extract pgroup value

Cases:
1. pgroup value is 'true' => 0
2. pgroup value is kind of true => Rubinius will try coerce_to Integer
3. pgroup value if kind of true and pass coerce then Rubinius will check
check whether the value is < 0. If yes then an ArgumentError exception is thrown
4. pgroup if kind of false (false, nil) - default behavior (like without
pgroup)

Fixes #1894
Merge pull request #1895 from LTe/process_spawn

Process spawn should not raise NoMethodError when true argument is given to :pgroup
Ignore block device test.
Fixed DESTDIR.
Don't load other Hash when enabling HAMT. Fixes #1926.
Prevent exception when --preserve-prefix is used without --prefix.
Merge pull request #1927 from voxik/fix-preserve-prefix

Prevent exception when --preserve-prefix is used without --prefix.
Merge pull request #1885 from ryoqun/thread-raise-deadlock

Completely fix deadlocks of Thread#raise
Merge pull request #1868 from IPGlider/master

Fix BlockArgument bytecode generation
Ignore -K options on non 1.8 versions

Fixes #1925
Add spec for not prefixing toplevel const_missing with Object::
Only prefix const_missing in the message of it's not in Object

Fixes #1922
Add specs for rb_block_call
Use LockGuards where appropriate as RAII
Correctly implement Thread#kill

Re-implement Thread#kill by adding new RaiseReason rather than complicating the
existing ad-hoc way of raising Exceptions.

Conceputually, Thread#kill isn't quite like exceptions. If the exception approach
wasn't replaced, it would be neccesary to really specially handle Thread::Die.

Make some failing specs pass. Also, Fix #864.
Implement 1.8 specific Thread#kill behavior
Implement rb_block_call

Fixes #1787
Merge pull request #1882 from ryoqun/thread-kill

Correctly implement Thread#kill
Better spec for default exception message of const_missing