purge all references to pth lib, gnupg only uses npth now
standardize build-stamp usage in external/Makefile

This is an attempt at making build dependencies work better, so that it
doesn't rebuild everything every time.
set min platform to android-14/4.0/Ice Cream Sandwich

Its currently too much work for us to handle supporting older versions.
This relies on a lot of new APIs both in the SDK, like the Contacts
handling, and in the NDK, with things like missing pthread_atfork():

http://bugs.g10code.com/gnupg/issue1576

Update target to the latest while I'm at it.
bump version to 0.3 code 4
include all CPU-specific JNI build folders
make compile error whenever there is a security issue with formats

-Wformat -Werror=format-security
add Posix.symlink() for making symlinks with needing `ln -s`

We have no guarantee that `ln -s` will be included in all Android distros,
but since most provide `ln -s`, I think we can be resonably sure that the
libc everywhere will include symlink().

Its also really a pain to run shell commands in Java for simple things like
this.
more reliable integration of Android NDK build files into external/Makefile

Now the build target for SDK, NDK, and external/Makefile are all set from
AndroidManifest.xml.

refs #1630
use NDK gcc 4.8 compiler, required NDK r9b or newer
`make gitclean` should not delete files that are committed into git
add Android support commit to m4/libtool.m4 on any project that uses it

This required some hacks since libassuan, libgpg-error, and npth didn't work
with just adding the m4/libtool.m4 to them.  They include some custom versions
of the autotools files, so those got blown away by using autoreconf.

refs #1548
sed hack to force libtool update for libgpg-error

For whatever reason, the libgpg-error autotools customizations where
especially troublesome.  So I just wrote some sed patterns to replace the
necessary things in libgpg-error/libtool.  libtool is just a generated shell
script after all...

refs #1548
install libs built Android-style into libs/$(APP_ABI)/ instead of assets/

This means that Android handles the rest for us, including bundling and
unpacking them from the APK, setting the LD_LIBRARY_PATH, etc.

refs #1548