Fairly major change: emit fixed sized allocas in the entry block as a variable,

Fairly major change: emit fixed sized allocas in the entry block as a variable,
instead of a variable pointer and an alloca.  All accesses to the variable then
use the address-of operator to access it.  This plays better with the internal
GCC code generation phases, which bail early on functions which contain allocas.
It also makes the code a bit easier to read.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6734 91177308-0d34-0410-b5e6-96231b3b80d8