Android patch 20140623

Things to improve in later versions (or now if someone knows a better way):
  * wchar conversion
  * Hack detection
  * Better way to replace builtin formspecs, maybe add Lua API functions
  * Other things you find in there ;-)

### Building

#### Debug:
```
cd build/android
make
<Answer questions>
```
#### Release:
```
<prepare keystore>
cd build/android
make release
<Answer questions>
<enter password when prompted>
```
This should probably be `org.minetest.minetest` or the like, to allow for other Minetest-related apps.