Sorry, my bad, I got the package name mixed up. The output of 'dpkg -S libGL.so.1' is:
libgl1-mesa-glx:i386: /usr/lib/i386-linux-gnu/libGL.so.1
libgl1-mesa-glx:i386: /usr/lib/i386-linux-gnu/libGL.so.1.2.0
libgl1-mesa-glx:amd64: /usr/lib/x86_64-linux-gnu/libGL.so.1
libgl1-mesa-glx:amd64: /usr/lib/x86_64-linux-gnu/libGL.so.1.2.0
And the output of 'ldd /usr/bin/glxinfo' is:
linux-vdso.so.1 (0x00007fff9a3fe000)
libGLEW.so.1.10 => /usr/lib/x86_64-linux-gnu/libGLEW.so.1.10 (0x00007f0f30079000)
libGLU.so.1 => /usr/lib/x86_64-linux-gnu/libGLU.so.1 (0x00007f0f2fe0b000)
libGL.so.1 => /usr/lib/libGL.so.1 (0x00007f0f2fb89000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f0f2f886000)
libX11.so.6 => /usr/lib/x86_64-linux-gnu/libX11.so.6 (0x00007f0f2f54b000)
libXext.so.6 => /usr/lib/x86_64-linux-gnu/libXext.so.6 (0x00007f0f2f338000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f0f2ef8f000)
libXmu.so.6 => /usr/lib/x86_64-linux-gnu/libXmu.so.6 (0x00007f0f2ed75000)
libXi.so.6 => /usr/lib/x86_64-linux-gnu/libXi.so.6 (0x00007f0f2eb64000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f0f2e860000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f0f2e64a000)
libXxf86vm.so.1 => /usr/lib/x86_64-linux-gnu/libXxf86vm.so.1 (0x00007f0f2e443000)
libXdamage.so.1 => /usr/lib/x86_64-linux-gnu/libXdamage.so.1 (0x00007f0f2e240000)
libXfixes.so.3 => /usr/lib/x86_64-linux-gnu/libXfixes.so.3 (0x00007f0f2e03a000)
libdrm.so.2 => /usr/lib/x86_64-linux-gnu/libdrm.so.2 (0x00007f0f2de2d000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f0f2dc10000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f0f2da0c000)
libxcb.so.1 => /usr/lib/x86_64-linux-gnu/libxcb.so.1 (0x00007f0f2d7ec000)
/lib64/ld-linux-x86-64.so.2 (0x00007f0f30332000)
libXt.so.6 => /usr/lib/x86_64-linux-gnu/libXt.so.6 (0x00007f0f2d586000)
libXau.so.6 => /usr/lib/x86_64-linux-gnu/libXau.so.6 (0x00007f0f2d381000)
libXdmcp.so.6 => /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007f0f2d17c000)
libSM.so.6 => /usr/lib/x86_64-linux-gnu/libSM.so.6 (0x00007f0f2cf75000)
libICE.so.6 => /usr/lib/x86_64-linux-gnu/libICE.so.6 (0x00007f0f2cd59000)
libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007f0f2cb54000)