Exception#set_backtrace

Specs fixed:

Exception#set_backtrace
- accepts an Array of Strings
- allows the user to set the backtrace from a rescued exception
- accepts an empty Array
- accepts a String
- accepts nil
- raises a TypeError when when passed a Symbol
- raises a TypeError when the Array contains a Symbol
Add w_backtrace to attributes
Use is_kind_of
Merge pull request #683 from krekoten/exception_set_backtrace

Exception#set_backtrace
Exception#==

Specs fixed:

Exception#==
- returns true if one exception is the dup'd copy of the other
- returns true if both exceptions have the same class, no message, and no backtrace
- returns true if both exceptions have the same class, the same message, and no backtrace
- returns true if both exceptions have the same class, the same message, and the same backtrace
- returns true if the two exceptions inherit from Exception but have different classes
- returns true if the two objects subclass Exception and have the same message and backtrace
- returns false if the two exceptions differ only in their backtrace
- returns false if the two exceptions differ only in their message
Merge pull request #685 from krekoten/exception_equal_value

Exception#==
space.send now takes a string, instead of a W_SymbolObject
Merge branch 'master' into exception_to_s
Send string instead of W_SymbolObject