* Enable the use of escaped literal strings

* Unresolved variable names now have the correct line number for their
  error messages
* Rename Def* to Value*
* Check for symbol table collisions before inserting values
* Remove the STRING keyword
* Enable the use of string literals to initialize constant arrays
* Enable the use of extended constants in more locations: eg ret [int] [4, 5]
* Allow method prototypes to appear in the constant pool of the program
* Support varargs methods better.  Enable varargs methods with 0 fixed
  arguments
* Allow the entire method prototype to optionally be specified in a call inst

llvm-svn: 321