lib: Introduce versioned symbols

As rpm-ostree evolves, it keeps driving API additions to libostree.
This creates a relatively tight coupling.

However, if delivering via e.g. RPM, unless one manually remembers to
increment the `Requires:` in the spec file, it's possible for the two
to become desynchronized.

RPM handles versioned symbols and will ensure a dependency if the
application starts using a newer version.

To implement this, switch to `-fvisibility=hidden`, along with an
annotation in the header, and finally add a `.sym` file.

This matches what other projects like systemd and libvirt do.

Although rather than attempting to retroactively version symbols, glom
them all onto the current one.

src/libostree/ostree-deployment.h

@@ -30,11 +30,15 @@ G_BEGIN_DECLS
 
 typedef struct _OstreeDeployment OstreeDeployment;
 
+_OSTREE_PUBLIC
 GType ostree_deployment_get_type (void) G_GNUC_CONST;
 
+_OSTREE_PUBLIC
 guint ostree_deployment_hash (gconstpointer v);
+_OSTREE_PUBLIC
 gboolean ostree_deployment_equal (gconstpointer ap, gconstpointer bp);
 
+_OSTREE_PUBLIC
 OstreeDeployment * ostree_deployment_new (int    index,
                                   const char  *osname,
                                   const char  *csum,
@@ -42,22 +46,36 @@ OstreeDeployment * ostree_deployment_new (int    index,
                                   const char  *bootcsum,
                                   int    bootserial);
 
+_OSTREE_PUBLIC
 int ostree_deployment_get_index (OstreeDeployment *self);
+_OSTREE_PUBLIC
 const char *ostree_deployment_get_osname (OstreeDeployment *self);
+_OSTREE_PUBLIC
 int ostree_deployment_get_deployserial (OstreeDeployment *self);
+_OSTREE_PUBLIC
 const char *ostree_deployment_get_csum (OstreeDeployment *self);
+_OSTREE_PUBLIC
 const char *ostree_deployment_get_bootcsum (OstreeDeployment *self);
+_OSTREE_PUBLIC
 int ostree_deployment_get_bootserial (OstreeDeployment *self);
+_OSTREE_PUBLIC
 OstreeBootconfigParser *ostree_deployment_get_bootconfig (OstreeDeployment *self);
+_OSTREE_PUBLIC
 GKeyFile *ostree_deployment_get_origin (OstreeDeployment *self);
 
+_OSTREE_PUBLIC
 void ostree_deployment_set_index (OstreeDeployment *self, int index);
+_OSTREE_PUBLIC
 void ostree_deployment_set_bootserial (OstreeDeployment *self, int index);
+_OSTREE_PUBLIC
 void ostree_deployment_set_bootconfig (OstreeDeployment *self, OstreeBootconfigParser *bootconfig);
+_OSTREE_PUBLIC
 void ostree_deployment_set_origin (OstreeDeployment *self, GKeyFile *origin);
 
+_OSTREE_PUBLIC
 OstreeDeployment *ostree_deployment_clone (OstreeDeployment *self);
 
+_OSTREE_PUBLIC
 char *ostree_deployment_get_origin_relpath (OstreeDeployment *self);
 
 G_END_DECLS