meson: Use declare_dependency for libraries

Now example binaries and tests don't have to be aware of the nuances for
configuring the build to use the library. This makes the project library
look like any other system dependency.

Change-Id: I9bbf33d32057964011fd8387e742e0d92117f848
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/example/meson.build b/example/meson.build
index 815a78f..8762e3b 100644
--- a/example/meson.build
+++ b/example/meson.build
@@ -3,7 +3,6 @@
 
 foreach example : examples
   executable(example, example + '.cpp',
-             include_directories: includes,
              implicit_include_directories: false,
-             link_with: stdplus)
+             dependencies: stdplus)
 endforeach