For All These Bugs:

PR645
PR761
PR1082
PR1122

Completely rewrite llvm-upgrade. This should be its final design. Any future
changes will use this same design.  The changes involve the following:

1. Make this work very much like the 1.9 AsmParser
2. Retain old upgrades dating back to release 1.2 time frame.
3. Merge in some of the upgrades between 1.9 and 2.0 (e.g. icmp/fcmp).
4. Attach a Signedness value (Signless, Unsigned, Signed) to every type,
   Value, Constant, Instruction, and list of those things in the Parser.
   Use these to make signedness decisions for instruction upgrades.
5. Implement unique name upgrade for function values and global values.
6. Identify rename cases that might cause problems and warn about them.
   For example: renaming a global variable with external linkage.
7. Generate a 2.0 IR using VMCore. This is necessary for numerous
   reasons and has the advantage that it never goes out of date.
8. Use the AsmPrinter to make the output nice.
9. Clean up error and warning messages from 1.9 form.

llvm-svn: 33531