ndk: Remove obsolete platform files

Remove the prebuilt system shared libraries and unified symbol files
from development/ndk. We don't need them anymore:

  - the unified symbol files are replaced by separate functions/variables
    symbol list, which were added in a previous commit, i.e.:

	libc.so.txt  --> libc.so.functions.txt
	                 libc.so.variables.txt

 - the shared libraries are now generated on the fly by the NDK
   gen-platforms.sh script, from the functions/variables symbol lists.

Note that we need to keep the static libraries and runtime objects,
they are required to build the cross-toolchains and target binaries.

Change-Id: Ifa0a7f2d741ed32b80216561ca3f17e67df06ce9
51 files changed