Load system extractor plugins from /system|vendor/lib[64]/extractors.

Plugins will be placed under /system|vendor/lib[64]/extractors and the
device will include a stub MediaComponents apk for later update.

Test: boots and play mp4 files
Bug: 67908547
Change-Id: I5ab30093d9dd50324ba327baa8270a204e10f8a5
diff --git a/services/mediaextractor/Android.mk b/services/mediaextractor/Android.mk
index 4980316..9f3746f 100644
--- a/services/mediaextractor/Android.mk
+++ b/services/mediaextractor/Android.mk
@@ -21,6 +21,16 @@
 
 # extractor libraries
 LOCAL_REQUIRED_MODULES := \
+    libaacextractor \
+    libamrextractor \
+    libflacextractor \
+    libmidiextractor \
+    libmkvextractor \
+    libmp3extractor \
+    libmp4extractor \
+    libmpeg2extractor \
+    liboggextractor \
+    libwavextractor \
     MediaComponents \
 
 LOCAL_SRC_FILES := main_extractorservice.cpp