Fix valadoc ;-)

So "./autogen.sh --enable-docs && make" gives me the following build error on a fresh tree. I know you committed some other fixes but this one has me stumped...

Making all in tests
make[2]: Entering directory `/home/robru/Applications/libfriends/libfriends/tests'
Making all in vala
make[3]: Entering directory `/home/robru/Applications/libfriends/libfriends/tests/vala'
  VALAC test_vala_vala.stamp
test-vala.vala:27.21-27.52: warning: local variable `service' declared but never used
    Friends.Service service = new Friends.Service ();
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
test-vala.vala:35.19-35.46: warning: local variable `utils' declared but never used
    Friends.Utils utils = new Friends.Utils ();
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
test-vala.vala:45.9-45.23: warning: local variable `m' declared but never used
    var m = new Main ();
        ^^^^^^^^^^^^^^^
Compilation succeeded - 3 warning(s)
  CC test_vala-test-utils.o
test-utils.c: In function ‘friends_test_utils_suite_construct’:
test-utils.c:110:2: warning: passing argument 3 of ‘g_test_add_data_func’ from incompatible pointer type [enabled by default]
In file included from /usr/include/glib-2.0/glib.h:84:0,
                 from test-utils.c:23:
/usr/include/glib-2.0/glib/gtestutils.h:108:9: note: expected ‘GTestDataFunc’ but argument is of type ‘void (*)(void *)’
test-utils.c:111:2: warning: passing argument 3 of ‘g_test_add_data_func’ from incompatible pointer type [enabled by default]
In file included from /usr/include/glib-2.0/glib.h:84:0,
                 from test-utils.c:23:
/usr/include/glib-2.0/glib/gtestutils.h:108:9: note: expected ‘GTestDataFunc’ but argument is of type ‘void (*)(void *)’
test-utils.c:112:2: warning: passing argument 3 of ‘g_test_add_data_func’ from incompatible pointer type [enabled by default]
In file included from /usr/include/glib-2.0/glib.h:84:0,
                 from test-utils.c:23:
/usr/include/glib-2.0/glib/gtestutils.h:108:9: note: expected ‘GTestDataFunc’ but argument is of type ‘void (*)(void *)’
test-utils.c:113:2: warning: passing argument 3 of ‘g_test_add_data_func’ from incompatible pointer type [enabled by default]
In file included from /usr/include/glib-2.0/glib.h:84:0,
                 from test-utils.c:23:
/usr/include/glib-2.0/glib/gtestutils.h:108:9: note: expected ‘GTestDataFunc’ but argument is of type ‘void (*)(void *)’
  CC test_vala-test-vala.o
  CCLD test-vala
make[3]: Leaving directory `/home/robru/Applications/libfriends/libfriends/tests/vala'
make[3]: Entering directory `/home/robru/Applications/libfriends/libfriends/tests'
make[3]: Nothing to be done for `all-am'.
make[3]: Leaving directory `/home/robru/Applications/libfriends/libfriends/tests'
make[2]: Leaving directory `/home/robru/Applications/libfriends/libfriends/tests'
Making all in docs
make[2]: Entering directory `/home/robru/Applications/libfriends/libfriends/docs'
  GEN friends-gtk-doc
error: Package `glib-2.0' not found in specified Vala API directories or GObject-Introspection GIR directories
error: glib-2.0 not found in specified Vala API directories
error: Package `gobject-2.0' not found in specified Vala API directories or GObject-Introspection GIR directories
error: gobject-2.0 not found in specified Vala API directories
error: Package `gio-unix-2.0' not found in specified Vala API directories or GObject-Introspection GIR directories
error: gio-unix-2.0, dependency of accounts, not found in specified Vala API directories
error: Package `gobject-2.0' not found in specified Vala API directories or GObject-Introspection GIR directories
error: Package `gobject-2.0' not found in specified Vala API directories or GObject-Introspection GIR directories
error: Package `gio-2.0' not found in specified Vala API directories or GObject-Introspection GIR directories
error: Package `gio-2.0' not found in specified Vala API directories or GObject-Introspection GIR directories
error: Package `json-glib-1.0' not found in specified Vala API directories or GObject-Introspection GIR directories
error: Package `json-glib-1.0' not found in specified Vala API directories or GObject-Introspection GIR directories
Failed: 12 error(s), 0 warning(s)
make[2]: *** [friends-gtk-doc] Error 1
make[2]: Leaving directory `/home/robru/Applications/libfriends/libfriends/docs'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/robru/Applications/libfriends/libfriends'
make: *** [all] Error 2

(build succeeds if I do "./autogen.sh --disable-docs && make")