Update gen-blueprints for ndk_library.

Change the module naming scheme from ndk_lib${NAME}.$VERSION to
lib${NAME}.ndk.$VERSION so soong doesn't complain that all shared libs
need to start with "lib". This has the added benefit of making our
libraries look like normal versioned shared libraries, e.g. libc.so.9
instead of ndk_libc.9.

Also, stop generating modules for anthing before Gingerbread.
Those are dead.

Test: make checkbuild
Bug: http://b/27533932
Change-Id: I5f1ade448c49af65ff98decad27786147c0fb04d
diff --git a/gen-blueprints.py b/gen-blueprints.py
index 093a13b..d9276ec 100755
--- a/gen-blueprints.py
+++ b/gen-blueprints.py
@@ -80,7 +80,7 @@
 
 def gen_lib_prebuilt(prebuilt, name, version):
     return ('ndk_prebuilt_library {{\n'
-            '    name: "ndk_{name}.{version}",\n'
+            '    name: "{name}.ndk.{version}",\n'
             '    defaults: ["ndk_{version}_defaults"],\n'
             '}}'.format(name=name, version=version))
 
@@ -97,6 +97,9 @@
     for prebuilt in get_prebuilts(names):
         name = os.path.splitext(os.path.basename(prebuilt))[0]
         version = sdk_version_from_path(prebuilt)
+        if version < 9:
+            # We don't support anything before Gingerbread any more.
+            continue
         prebuilts.append(fn(prebuilt, name, version))
     return prebuilts