>> Sorry, forgot to mention that you should copy the files
>> into
>> libcarddav-0.6.2/ instead of admin.  Also, you
>> shouldn't run the make -f
>> admin command.
>
> FTBFS.
>
> Here is what I ran:
>
> find ./ -name Makefile.in -exec rm -f {} \;
> cp -p /usr/share/aclocal/libtool.m4 ./libtool.m4.in
> cp -p /usr/share/libtool/ltmain.sh ./ltmain.sh
> ./autogen.sh
>

Unfortunately I cannot help any more on this one; I just built the package
on my CentOS 5 system without any problems, so the problem seems to be
isolated to Slackware.  If it helps with your debugging, make isn't even
entering the src subdirectory to compile the sources therein (?!??). 
Maybe other libraries have experienced a similar build failure on
Slackware in the past?  You could try manually entering the src/ directory
and running make from there...

Tim