Remove the dependency on libc

Recent versions of bindgen use `std::os::raw` over `libc`, but currently
`libsqlite3-sys` is overriding that. `std::os::raw` is a subset of
`libc` that exports only the relevant type definitions, but not any
functions which require additional linking. This enables
`libsqlite3-sys` to be more easily used on targets that may not have a
libc available (presumably sqlite itself would have been compiled with
musl in that case)

libsqlite3-sys/build.rs

@@ -27,7 +27,6 @@ fn run_bindgen<T: Into<String>>(header: T) {
     let mut output = Vec::new();
     bindgen::builder()
         .header(header.clone())
-        .ctypes_prefix("::libc")
         .type_chooser(Box::new(SqliteTypeChooser))
         .generate()
         .expect(&format!("could not run bindgen on header {}", header))