Add platform infrastructure for features.

This introduces a new mechanism to define features associated with
a platform, query the current device for the available features,
and enforce that apps requiring features that aren't available can't
be installed.

Also now allows uses-library to specify that a library is optional,
so the lack of such a library will not prevent the app from being
installed (but if it does exist it will be correctly linked into
the app).

Change-Id: I5b369b46cfa0b3d37c9e08fd14ef1098a978e67b
diff --git a/tools/aapt/Command.cpp b/tools/aapt/Command.cpp
index f4afd7f..790b474 100644
--- a/tools/aapt/Command.cpp
+++ b/tools/aapt/Command.cpp
@@ -730,8 +730,6 @@
                     } else if (tag == "uses-permission") {
                         String8 name = getAttribute(tree, NAME_ATTR, &error);
                         if (error == "") {
-                            int opt = getIntegerAttribute(tree,
-                                    REQUIRED_ATTR, NULL, 1);
                             if (name == "android.permission.CAMERA") {
                                 hasCameraPermission = true;
                             }
@@ -772,7 +770,10 @@
                             fprintf(stderr, "ERROR getting 'android:name' attribute for uses-library: %s\n", error.string());
                             goto bail;
                         }
-                        printf("uses-library:'%s'\n", libraryName.string());
+                        int req = getIntegerAttribute(tree,
+                                REQUIRED_ATTR, NULL, 1);
+                        printf("uses-library%s:'%s'\n",
+                                req ? "" : "-not-required", libraryName.string());
                     } else if (tag == "receiver") {
                         withinReceiver = true;
                         receiverName = getAttribute(tree, NAME_ATTR, &error);