Implement optional JPEG2000 codec adapter (#40)

crates/libremetaverse-openjpeg/build.rs

@@ -0,0 +1,16 @@
+use std::env;
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+    let target = env::var("TARGET").expect("Cargo provides TARGET");
+    if target.contains("msvc") {
+        vcpkg::Config::new()
+            .find_package("openjpeg")
+            .expect("jpeg2000 requires OpenJPEG 2.5.4 or newer from vcpkg");
+    } else {
+        pkg_config::Config::new()
+            .atleast_version("2.5.4")
+            .probe("libopenjp2")
+            .expect("jpeg2000 requires pkg-config and OpenJPEG 2.5.4 or newer");
+    }
+}