#52 Install destination not relocatable breaking packaging

[Dagobert Michelsen]

I am packaging up mod_auth_kerb 5.4 on Solaris with Sun Studio 12. This requires installation to a relocated directory. To set this I slightly changed the Makefile in a few ways:
1. On install "-c" should not be used or the sources will be compiled twice
2. The SPNEGO_SRCS on install confuse apxs from Apache 2.2.16
3. On installation only mod_auth_kerb.la should be installed
4. This made me notice the name is hardwired in apxs.sh instead of using $6

The changes are bundled in the attached patch.

[Dagobert Michelsen]