ART: Wire up DexToDexCompiler without extern

The extern declaration actually had the wrong signature, a parameter
was missing, and we never noticed.

Remove the function field and extern. Add a header for the compiler.
Use the header file.

Change-Id: Ia4d4dd86211da6045709a45c7bf8430471d1b62b
diff --git a/compiler/Android.mk b/compiler/Android.mk
index 3947078..4944915 100644
--- a/compiler/Android.mk
+++ b/compiler/Android.mk
@@ -171,6 +171,7 @@
   dex/quick/mips/mips_lir.h \
   dex/quick/resource_mask.h \
   dex/compiler_enums.h \
+  dex/dex_to_dex_compiler.h \
   dex/global_value_numbering.h \
   dex/pass_me.h \
   driver/compiler_driver.h \