autotools: ensure that link lines are complete

As mentioned by Tino Keitel on the mailing list, some libs and
executables were only implicitly linked against libraries that they
called directly. This happened to work by chance because these libraries
ended up in the running executable anyway, due to indirect loading.

To catch such problems, the "make installcheck" was extended:
dpkg-shlibdeps is run, if available, and the error output is scanned
for the messages which indicate that a symbol is used without linking
to the right library (example output below).

Had to fix quite a few _LIBADD lines to pass the test.
Some exceptions are allowed:
- libsmltk depends on the caller providing SySync logging support.
- libneon is intentionally not linked explicitly for syncevolution.org
  binaries, to make resulting binaries work with GNUTLS and OpenSSL.

dpkg-shlibdeps: warning: debian/syncevolution-libs/usr/lib/syncevolution/backends/syncdav.so contains an unresolvable reference to symbol icalparameter_new_from_value_string: it's probably a plugin.
dpkg-shlibdeps: warning: 51 other similar warnings have been skipped (use -v to see them all).
...
dpkg-shlibdeps: warning: symbol dlsym used by debian/libsyncevolution0/usr/lib/libsyncevolution.so.0.0.0 found in none of the libraries.
dpkg-shlibdeps: warning: symbol dlerror used by debian/libsyncevolution0/usr/lib/libsyncevolution.so.0.0.0 found in none of the libraries.
dpkg-shlibdeps: warning: symbol dlopen used by debian/libsyncevolution0/usr/lib/libsyncevolution.so.0.0.0 found in none of the libraries.

1 files changed, 1 insertions, 0 deletions

diff --git a/po/POTFILES.skip b/po/POTFILES.skip
index 00534cd9..ea197269 100644
--- a/po/POTFILES.skip
+++ b/po/POTFILES.skip
@@ -1,2 +1,3 @@
 src/gtk-ui/ui.xml
 src/gtk-ui/gtkinfobar.c
+src/synthesis/src/pcre/pcre_compile.c