Remove headers from LOCAL_SRC_FILES

The build system does not use headers in LOCAL_SRC_FILES. To prevent
typos, it's becoming a warning to add something to LOCAL_SRC_FILES that
is not used. Since these lists are coming from file shared with other
Makefile systems, use filter-out to do this dynamically. Once we move to
Soong, we will need our own lists though - Soong cannot read makefiles.

Remove LOCAL_EXPORT_C_INCLUDE_DIR entries that do not exist.

Also clean up LOCAL_C_INCLUDES -- with LOCAL_EXPORT_C_INCLUDE_DIRS and
the default $(LOCAL_PATH) entry, most were not necessary.

Remove LOCAL_MODULE_TAGS := optional, that's the default.

Change-Id: I2d77814eb227371da2945f6aede671d9f66d7b09