Add a testcase for checking the integer-promotion of many different vector

Add a testcase for checking the integer-promotion of many different vector
types (with power of two types such as 8,16,32 .. 512).

Fix a bug in the integer promotion of bitcast nodes. Enable integer expanding
only if the target of the conversion is an integer (when the type action is
scalarize).

Add handling to the legalization of vector load/store in cases where the saved
vector is integer-promoted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132985 91177308-0d34-0410-b5e6-96231b3b80d8