For PR1248:

Eliminate support for type planes in numbered values. This simplifies the
data structures involved in managing forward definitions, etc. Instead of
requiring maps from type to value, we can now just use a vector of values.
These changes also required rewrites of some support functions such as
InsertValue, getBBVal, and ResolveDefinitions. Some other cosmetic changes
were made as well.

llvm-svn: 35173