curl for android demo.

how to generate libcurl:
1. edit jni/configure.sh, change the default settings:
   read the script carefully..normally you can keep it as is
2. run jni/configure.sh
   if there are any error, check and fix...
3. run ndk-build, generate libcurl.so

libcurl.so size:
   (default is https with ares)
   https: ~169K (including http, https)
    ares: ~28K (adding to https, with ares support)
    ipv6: ~0K (no extra size)
   +full: ~278K (all protocols, with ares)