Copy llvm2py.py to pllvm.py, preparing to split off LLVM dependencies.
Remove code which depends on llvm module.
Use pllvm module.
Start adding native versions of LLVM attributes.
Support load instruction, include load getelementptr extension.

load getelementptr i8* %p, i32 10 is a representation of common
textbook MEM[p + 10], i.e. indexed with offset addressing mode
(with strict LLVM IR this would be 2 operations). Again, reason
of support is 1-to-1 translation of textbook examples.
Render extended "load getelementptr" insttruction.
Refactor PGlobalVariable constructor.
Support global vars.
Add parsing testcase with global, load, load elementptr.