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.

This is a squashed commit based on an initial change with a couple of
fixes to avoid breaking certain targets. The source commits are:
  d723bd7669b4fc88dc282d8bf8ba5ecb2849d22f
  00d504c06ea034befe143e6b8cb34d004670ed02
  429ba89cd293633d2f882165066b422c96597df2

Change-Id: I034abec27bf4020d84af60d7acc1939c59986dd6
diff --git a/libs/gui/SurfaceControl.cpp b/libs/gui/SurfaceControl.cpp
index 61011b9..1983027 100644
--- a/libs/gui/SurfaceControl.cpp
+++ b/libs/gui/SurfaceControl.cpp
@@ -89,12 +89,12 @@
     return lhs->mHandle == rhs->mHandle;
 }
 
-status_t SurfaceControl::setLayerStack(int32_t layerStack) {
+status_t SurfaceControl::setLayerStack(uint32_t layerStack) {
     status_t err = validate();
     if (err < 0) return err;
     return mClient->setLayerStack(mHandle, layerStack);
 }
-status_t SurfaceControl::setLayer(int32_t layer) {
+status_t SurfaceControl::setLayer(uint32_t layer) {
     status_t err = validate();
     if (err < 0) return err;
     return mClient->setLayer(mHandle, layer);