Fix libtoxav linking issue

Removed some whitespaces and fix linking issue.

Original:
```shell
% ldd libtoxav.so.0.0.0
        linux-vdso.so.1 (0x00007fff351fe000)
        libsodium.so.4 => /usr/lib/libsodium.so.4 (0x00007fc0e4743000)
        libm.so.6 => /usr/lib/libm.so.6 (0x00007fc0e4442000)
        libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007fc0e4225000)
        libc.so.6 => /usr/lib/libc.so.6 (0x00007fc0e3e7c000)
        /usr/lib64/ld-linux-x86-64.so.2 (0x00007fc0e4bdd000)
```

But instead it should have been
```shell
% ldd libtoxav.so.0.0.0
        linux-vdso.so.1 (0x00007fff05bfe000)
        libopus.so.0 => /usr/lib/libopus.so.0 (0x00007f8bc2c74000)
        libvpx.so.1 => /usr/lib/libvpx.so.1 (0x00007f8bc2890000)
        libtoxcore.so.0 => /home/aitjcize/Work/tox/dist/lib/libtoxcore.so.0 (0x00007f8bc266c000)
        libsodium.so.4 => /usr/lib/libsodium.so.4 (0x00007f8bc2416000)
        libm.so.6 => /usr/lib/libm.so.6 (0x00007f8bc2115000)
        libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007f8bc1ef8000)
        libc.so.6 => /usr/lib/libc.so.6 (0x00007f8bc1b4f000)
        /usr/lib64/ld-linux-x86-64.so.2 (0x00007f8bc3106000)
```

toxav/Makefile.inc

the libtoxav_la_LIBS should be libtoxav_la_LIBADD