Update winapi requirement from 0.2 to 0.3 (#537)

* Update winapi requirement from 0.2 to 0.3

Updates the requirements on [winapi](https://github.com/retep998/winapi-rs) to permit the latest version.
- [Release notes](https://github.com/retep998/winapi-rs/releases)
- [Commits](https://github.com/retep998/winapi-rs/commits/0.3.7)

Signed-off-by: dependabot[bot] <support@dependabot.com>

* Fixing upgrading winapi (hopefully).

Cargo.toml

@@ -54,7 +54,7 @@ murmurhash32 = "0.2"
 chrono = "0.4"
 
 [target.'cfg(windows)'.dependencies]
-winapi = "0.2"
+winapi = "0.3"
 
 [dev-dependencies]
 rand = "0.6"

src/directory/mmap_directory.rs

@@ -320,7 +320,7 @@ impl MmapDirectory {
         #[cfg(windows)]
         {
             use std::os::windows::fs::OpenOptionsExt;
-            use winapi::winbase;
+            use winapi::um::winbase;
 
             open_opts
                 .write(true)