Corrected build for android.

1. Corrected build for android.
2. Included --enable-android on configure script.
3. Build with that sample script:
```sh
#!/bin/sh
# Make sure you have TOOLCHAIN defined in .bashrc or .bash_profile and have linux/dvb headers in include dir.
SRC_DIR="`pwd`/tvheadend"
INCLUDE_DIR="`pwd`/out/include"
cd $SRC_DIR
export SYS_ROOT="$TOOLCHAIN/sysroot"
export CC="arm-linux-androideabi-gcc --sysroot=$SYS_ROOT -I$INCLUDE_DIR"
export CXX="arm-linux-androideabi-g++ --sysroot=$SYS_ROOT -I$INCLUDE_DIR"
export CPP="arm-linux-androideabi-cpp"
export LD="arm-linux-androideabi-ld"
export AR="arm-linux-androideabi-ar"
export RANLIB="arm-linux-androideabi-ranlib"
export STRIP="arm-linux-androideabi-strip"
export CROSSCOMPILE="arm-linux-androideabi-"
export CFLAGS="--sysroot=$SYS_ROOT -I$INCLUDE_DIR"
export CXXFLAGS="--sysroot=$SYS_ROOT -I$INCLUDE_DIR"
export LIBS="-lc -lgcc"
./configure --prefix=$SYS_ROOT/usr --arch=armv7  --platform=linux --disable-avahi --enable-bundle --python=/usr/bin/python --enable-android
make
```
**TODO: change shm code to ashmem on tvhtime.c**