Convert libdrmframework and drmserver to Android.bp

See build/soong/README.md for more information.

Also moves a few headers into the same library as their
implementation, and fixes a few includes to go through the
global frameworks/av/include path instead of manually adding
frameworks/av/include/drm.

Test: m -j checkbuild
Change-Id: I0c2d2f2262e7ed78d80a0d44795705c64b797ff0
diff --git a/drm/mediadrm/Android.bp b/drm/mediadrm/Android.bp
new file mode 100644
index 0000000..b9f07f1
--- /dev/null
+++ b/drm/mediadrm/Android.bp
@@ -0,0 +1 @@
+subdirs = ["plugins/*"]