Remove unnecessary exports from various libraries

This reduces library size by about 10-15%

Test: build, run CTS
Change-Id: I9ecb3f08a8bd6128e601656125e3523c0c52ddb6
diff --git a/media/libmedia/exports.lds b/media/libmedia/exports.lds
new file mode 100644
index 0000000..b09fbce
--- /dev/null
+++ b/media/libmedia/exports.lds
@@ -0,0 +1,7 @@
+{
+    global:
+        *;
+    local:
+        _ZN7android13MidiIoWrapper*;
+        _ZTVN7android13MidiIoWrapperE;
+};