AArch32: Use the shared scopes `CodeBufferCheckScope` and `EmissionCheckScope`.

This patch continues toward the goal of unifying code-generation scopes for all
backends.

The new scopes differ from the existing AArch32 mechanisms, so a few tests for
literal and veneer pools needed to be updated.

The patch also adds AArch32 tests for the new scopes.

Change-Id: Ia6a93e6e860b47e703b6c9034fefa405810c18a0
diff --git a/src/macro-assembler-interface.h b/src/macro-assembler-interface.h
index 205c957..87a4f84 100644
--- a/src/macro-assembler-interface.h
+++ b/src/macro-assembler-interface.h
@@ -33,7 +33,7 @@
 
 class MacroAssemblerInterface {
  public:
-  virtual internal::AssemblerBase* GetAssemblerBase() = 0;
+  virtual internal::AssemblerBase* AsAssemblerBase() = 0;
 
   virtual ~MacroAssemblerInterface() {}