Add specs for load and dump of String with ivars
Add spec for loading marshalled string with custom constructor
Don't use constructor but set class direct for custom strings

Fixes #2554
Fix dump spec for 1.8 mode
Don't check encoding in 1.8 mode
Fix marshalling in 1.8 mode for String
Revert "Disable fibers on >= 10.7. Fixes #815"

This reverts commit e70c097e4f58130efba7b5f845fba9e16ae3c4eb.

This should be enabled again, so for example Process.cpu_times works
properly for current thread timings. The original reason for this change
is a nonexistant reason now.
Fixed compilation on Mavericks broken by revert in b83a17b84.
No need to explictly mark as inlined, compiler will take care of it

The compiler is smart enough to see whether or not to inline this when
compiling source code, since it's available in the header anyway.
Replaced VLA with transient ByteArray.
Setup global symbol for respond_to_missing
Retry algorithm for when sysconf() fails

This uses a default buffer of size 2048 and does a retry if this is too
small. It also throws a proper exception if any other error happens. The
default of 2048 is based on defaults also used in FreeBSD itself:

http://lists.freebsd.org/pipermail/freebsd-bugs/2011-October/046141.html

Since there is no GC possible for the getpwnam_r call, we don't have to
use a pinned ByteArray. There is no gc lock guard here or a gctoken
passed down, so it can move during this system call. We also can use a
non zeroed version since it's written to immediately anyway.
Introduce creating a dirty Tuple

This can be used for cases where after the tuple is created, immediately
values are set. This results in not having to set all entries to nil
first if they are overwritten afterwards.
Add Array::create_dirty to use when setting elements immediately

In the interpreter we create array's in a bunch of places and
immediately set values, such as with make_array. This create_dirty
method allows for creating an Array with a dirty Tuple so we don't set
the data unnecessary twice.
Bounded getpwnam_r buffer size doubling.
Exposed ProfileFormatter for mspec help.
Fixed check to account for overflow.
Fixed loading encoding converter path cache.
Add additional cases for String#to_i benchmarks
Add spec for turning string into Bignum for String#to_i