Clean up lua docs scripts

- ldoc is now a git submodule
- ldoc can be installed using scripts/install.{sh,ps1}
- lua docs can be build using scripts/build.{sh,ps1}
- all lua docs-related files now reside inside of the docs folder

docs/scripts/install.ps1

@@ -0,0 +1,41 @@
+try {
+  cd $PSScriptRoot/..
+
+  $lua_binary = $env:LUA_BINARY
+  if ($lua_binary -eq $null) {
+    $lua_binary = "lua"
+  }
+
+  if ((Get-Command "$lua_binary" -ErrorAction SilentlyContinue) -eq $null) {
+    if ($env:LUA_BINARY -eq $null) {
+      echo "lua binary not found; please set `$LUA_BINARY manually."
+    } else {
+      echo "lua binary not found: $lua_binary"
+    }
+    exit 1
+  }
+
+  if ((Get-Command "luarocks" -ErrorAction SilentlyContinue) -eq $null) {
+    echo "luarocks not found"
+    exit 1
+  }
+
+  $lua_version = (Invoke-Expression -Command "& $lua_binary -v 2>&1") -Replace '^Lua (\d+)\.(\d+).*$','$1.$2'
+  echo "Detected lua version $lua_version"
+
+  $luarocks_args=@(
+    "--tree",
+    "$(Get-Location)/lua_modules",
+    "--lua-version",
+    "$lua_version"
+  )
+
+  try {
+    cd ./libs/ldoc
+    luarocks @luarocks_args make
+  } finally {
+    popd
+  }
+} finally {
+  popd
+}