Made two compile options dependent on whether or not the plugins are
selected.

Removed autoreconf as autools files are not being patched.

Added PKG_BUILD_PARALLEL for faster compilation.

Added patch to fix compilation with libjpeg-turbo. libjpeg-turbo can be
fixed to include this API, but it's probably better for size reasons to
patch libextractor instead.

Added -liconv since it seems to be needed for some reason.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Fixes compilation with -Wimplicit-function-declaration

Signed-off-by: Rosen Penev <rosenp@gmail.com>