Implement _CONFIG macro to allow users to se to configuration settings on the part.

Implement _CONFIG macro to allow users to se to configuration settings on the part.
Implement _section macro to allow users to place objects in specific sections.
Implement _address macro to allow users to place objects at a particular address.
Placing objects at a memory address:
crate a unique section name from varname, address, object type and put that section at specified address. Mark this section a full (size = banksize) so that other objects do not compete for it while placing objects to sections in AsmPrinter.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74822 91177308-0d34-0410-b5e6-96231b3b80d8