The crypt(3) function is not available in Android, so remove support
in ext for now.

diff -u -r ../picoLisp/src/ext.c ./src/ext.c
--- ../picoLisp/src/ext.c	2015-04-27 00:34:17.000000000 -0400
+++ ./src/ext.c	2015-11-27 06:07:18.767005597 -0500
@@ -252,6 +252,7 @@
 
 /*** Password hashing ***/
 // (Ext:Crypt 'key 'salt) -> str
+#ifndef __ANDROID__
 any Crypt(any x) {
    any y;
 
@@ -269,3 +270,4 @@
       }
    }
 }
+#endif