Fix non-autolinks warnings

src/vtab/array.rs

@@ -4,7 +4,7 @@
 //! define.
 //!
 //! Port of [carray](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/carray.c)
-//! C extension: https://www.sqlite.org/carray.html
+//! C extension: `https://www.sqlite.org/carray.html`
 //!
 //! # Example
 //!

src/vtab/csvtab.rs

@@ -1,7 +1,7 @@
 //! `feature = "csvtab"` CSV Virtual Table.
 //!
 //! Port of [csv](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/csv.c) C
-//! extension: https://www.sqlite.org/csv.html
+//! extension: `https://www.sqlite.org/csv.html`
 //!
 //! # Example
 //!

src/vtab/series.rs

@@ -2,7 +2,7 @@
 //!
 //! Port of C [generate series
 //! "function"](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/series.c):
-//! https://www.sqlite.org/series.html
+//! `https://www.sqlite.org/series.html`
 use std::default::Default;
 use std::marker::PhantomData;
 use std::os::raw::c_int;