C++: IR: Drop the aliased SSA

It is expensive, and has little benefit.

Author: igfoo

cpp/ql/lib/semmle/code/cpp/ir/IR.qll

@@ -42,6 +42,4 @@
  *   be represented as the `IRType` `uint4`, a four-byte unsigned integer.
  */
 
-// Most queries should operate on the aliased SSA IR, so that's what we expose
-// publicly as the "IR".
-import implementation.aliased_ssa.IR
+import implementation.unaliased_ssa.IR

cpp/ql/lib/semmle/code/cpp/ir/IRConsistency.ql

@@ -5,4 +5,4 @@
  * @id cpp/ir-consistency-check
  */
 
-import implementation.aliased_ssa.IRConsistency
+import implementation.unaliased_ssa.IRConsistency

cpp/ql/lib/semmle/code/cpp/ir/PrintIR.ql

@@ -5,4 +5,4 @@
  * @kind graph
  */
 
-import implementation.aliased_ssa.PrintIR
+import implementation.unaliased_ssa.PrintIR

cpp/ql/lib/semmle/code/cpp/ir/PrintIR.qll

@@ -8,4 +8,4 @@
  * to dump.
  */
 
-import implementation.aliased_ssa.PrintIR
+import implementation.unaliased_ssa.PrintIR

cpp/ql/lib/semmle/code/cpp/ir/ValueNumbering.qll

@@ -1 +1 @@
-import implementation.aliased_ssa.gvn.ValueNumbering
+import implementation.unaliased_ssa.gvn.ValueNumbering