docs: Get API docs working again

This changes around a few things that didn't work for me:
* Section names seem to be ostree-* instead of libostree-*
* Also XML files are ostree-* (they didn't show up at all)
- gtk-doc doesn't seem to parse const _OSTREE_PUBLIC correctly
* pull documentation is now on the actual functions rather than stubs
* Update gitignore with some more files

And there some changes to make gtk-doc give fewer warnings (not finished)

Closes: #327
Approved by: cgwalters

src/libostree/ostree-lzma-decompressor.c

@@ -29,6 +29,14 @@ enum {
   PROP_0,
 };
 
+/**
+ * SECTION:ostree-lzma-decompressor
+ * @title: LZMA decompressor
+ *
+ * An implementation of #GConverter that decompresses data using
+ * LZMA.
+ */
+
 static void _ostree_lzma_decompressor_iface_init          (GConverterIface *iface);
 
 struct _OstreeLzmaDecompressor