Install new singleton class when we don't match

Fixes #1886
Explicitly set tm_isdst before using timelocal64

When using timelocal64, we always want it to compute the DST and not use
what we provide. This happens on all platforms except OpenBSD by
default.

Fixes #1906
Add a proper construction to SymbolTable

This makes sure we initialize the necessary values
Merge pull request #1900 from lmars/fix-syslog-mask-spec

Fix Syslog mask spec
Merge pull request #1893 from voxik/destdir

Use DESTDIR environment variable to allow to specify custom installation...
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