ART: More warnings

Enable -Wno-conversion-null, -Wredundant-decls and -Wshadow in general,
and -Wunused-but-set-parameter for GCC builds.

Change-Id: I81bbdd762213444673c65d85edae594a523836e5
diff --git a/runtime/gc/allocator/rosalloc.h b/runtime/gc/allocator/rosalloc.h
index a2f8342..2a0bf10 100644
--- a/runtime/gc/allocator/rosalloc.h
+++ b/runtime/gc/allocator/rosalloc.h
@@ -616,6 +616,10 @@
 };
 std::ostream& operator<<(std::ostream& os, const RosAlloc::PageMapKind& rhs);
 
+// Callback from rosalloc when it needs to increase the footprint. Must be implemented somewhere
+// else (currently rosalloc_space.cc).
+void* ArtRosAllocMoreCore(allocator::RosAlloc* rosalloc, intptr_t increment);
+
 }  // namespace allocator
 }  // namespace gc
 }  // namespace art