libgui: Enable -Weverything and -Werror

Enables -Weverything and -Werror, with just a few exceptions for
warnings we can't (or shouldn't need to) work around.

Change-Id: I034abec27bf4020d84af60d7acc1939c59986dd6
diff --git a/include/gui/SurfaceComposerClient.h b/include/gui/SurfaceComposerClient.h
index 4cbfc09..37d953e 100644
--- a/include/gui/SurfaceComposerClient.h
+++ b/include/gui/SurfaceComposerClient.h
@@ -127,7 +127,7 @@
     status_t    show(const sp<IBinder>& id);
     status_t    setFlags(const sp<IBinder>& id, uint32_t flags, uint32_t mask);
     status_t    setTransparentRegionHint(const sp<IBinder>& id, const Region& transparent);
-    status_t    setLayer(const sp<IBinder>& id, int32_t layer);
+    status_t    setLayer(const sp<IBinder>& id, uint32_t layer);
     status_t    setAlpha(const sp<IBinder>& id, float alpha=1.0f);
     status_t    setMatrix(const sp<IBinder>& id, float dsdx, float dtdx, float dsdy, float dtdy);
     status_t    setPosition(const sp<IBinder>& id, float x, float y);