Update libtool to support Android.
* m4/libtool.m4: Add "linux*android*" case. Taken from the libgpg-error.
This is the libgpg-error commit
commit bf0d67dbfa4161e529781d6dfbfcce7126c3bf22 Author: David 'Digit' Turner <digit@google.com> Date: Tue Oct 22 14:26:53 2013 +0200