[ScopInfo] Do not add array name into memory reference ids

Before this change a memory reference identifier had the form:

  <STMT>_<ACCESSTYPE><ID>_<MEMREF>, e.g., Stmt_bb9_Write0_MemRef_tmp11

After this change, we use the format:

  <STMT>_<ACCESSTYPE><ID>, e.g., Stmt_bb9_Write0

The name of the array that is accessed through a memory reference is not
necessary to uniquely identify a memory reference, but was only added to
provide additional information for debugging. We drop this information now
for the following two reasons:

  1) This shortens the names and consequently improves readability
  2) This removes a second location where we decide on the name of a scop array,
     leaving us only with the location where the actual scop array is created.

Having after 2) only a single location to name scop arrays will allow us to
change the naming convention of scop arrays more easily, which we will do
in a future commit to reduce compilation time.

llvm-svn: 302004