allow building out of tree (sort of)

allow building out of tree (sort of)

the current configure script assumes that it will be run in the srcdir ... i
often build things out of tree so you can quickly punt all the generated
files:
mkdir build
cd build
../configure
cd ..
rm -r build
clean!

this tweaks the configure script in a few places to use the correct variable
instead of assuming that configure is always in $PWD ...

i say "sort of" in the subject because there is still the issues of the pcm
symbols list being generated in $builddir instead of $srcdir and the alsa
include symlink, but these doesnt really concern me for what i need ;)

Signed-off-by: Mike Frysinger <vapier@gentoo.org>