build: don't ship access syms files in tarball

build: don't ship access syms files in tarball

On a mingw VPATH build (such as done by ./autobuild.sh), the tarball
created by 'make dist' was including generated files.  The VPATH
rules were then seeing that the tarball files were up-to-date, and
not regenerating files locally, leading to this failure:

  GEN      libvirt.syms
cat: libvirt_access.syms: No such file or directory
cat: libvirt_access_qemu.syms: No such file or directory
cat: libvirt_access_lxc.syms: No such file or directory
make: *** [libvirt.syms] Error 1

We already have a category for generated sym files, which are
intentionally not part of the tarball; stick the access sym
files in that category.  The rearrange the declarations a bit
to make it harder to repeat the problem, dropping things that
are now redundant (for example, BUILT_FILES already includes
GENERATED_SYM_FILES, so it does not also need to call out
ACCESS_DRIVER_SYM_FILES).

* src/Makefile.am (USED_SYM_FILES): Don't include generated files.
(GENERATED_SYM_FILES): Access syms files are generated.
(libvirt.syms): Include access syms files here.
(ACCESS_DRIVER_SYMFILES): Rename...
(ACCESS_DRIVER_SYM_FILES): ...for consistency.

Signed-off-by: Eric Blake <eblake@redhat.com>