I have developed a commercial 2D animation program,
http://www.plasticanimationpaper.dk.  From our website, we offer a
Windows version and a Linux version of our program.  We want to make
sure that the Linux version will work on most newer Linux systems
(libc6 I guess).

I'm building the binary on a Mandrake 10.0 32bit system.

Our program makes use of libSDL (http://www.libsdl.org) version 1.2.9
as well as a number of other libraries.  To reduce the number of
dependencies, I'm linking statically with as much as I can, and an
'ldd' reveals there's little left that our binary requires from the
target machine:

Output of ldd ./pap
        linux-gate.so.1 =>  (0xffffe000)
        libXext.so.6 => /usr/X11R6/lib/libXext.so.6 (0x4002a000)
        libSM.so.6 => /usr/X11R6/lib/libSM.so.6 (0x40038000)
        libX11.so.6 => /usr/X11R6/lib/libX11.so.6 (0x40041000)
        libpthread.so.0 => /lib/tls/libpthread.so.0 (0x40123000)
        libaudio.so.2 => /usr/X11R6/lib/libaudio.so.2 (0x40133000)
        libasound.so.2 => /usr/lib/libasound.so.2 (0x4014a000)
        libdl.so.2 => /lib/libdl.so.2 (0x401f8000)
        libXi.so.6 => /usr/X11R6/lib/libXi.so.6 (0x401fb000)
        libstdc++.so.5 => /usr/lib/libstdc++.so.5 (0x40203000)
        libm.so.6 => /lib/tls/libm.so.6 (0x402c3000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x402e6000)
        libc.so.6 => /lib/tls/libc.so.6 (0x402ef000)
        libICE.so.6 => /usr/X11R6/lib/libICE.so.6 (0x40438000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
        libXt.so.6 => /usr/X11R6/lib/libXt.so.6 (0x4044f000)

Most of this stuff is found virtually everywhere, except libaudio!  A
number of (potential) customers have complained that they don't have
libaudio, and this is quite frustrating for us.

My questions:

1)  How should I solve the libaudio problem?  I have no libaudio.a
file so I cannot statically link it into the final binary executable. 
Would this dependency go away if I built the program on another Linux
distro?  I can't believe it's libSDL itself that needs libaudio?

2)  A more general question: to cover "most" newer Linux distros, what
kind of binaries should we support, will libc6 32bit and 64bit be
enough? What about glibc6, is that the same as libc6?

I don't know what information I should provide, but please feel free
to ask for clarification.