Update rlua requirement from 0.15.0 to 0.19.4

[dependabot]

Updates the requirements on rlua to permit the latest version.

Changelog

Sourced from rlua's changelog.

[0.19.4]

• Fix the lua-no-oslib feature introduced with a bug in 0.19.3.

[0.19.3]

• Add new features lua-no-oslib to not compile in the os lib to the Lua library. Useful for targets (e.g. iOS) where the os lib is unavailable.

[0.19.2]

• Fix issue #253 (userdata types with alignment > 8 bytes could cause crashes)

[0.19.1]

• The -sys crates (bumped to 0.1.1) now use pregenerated bindgen outputs in the package instead of running bindgen at build time. This means that libclang is no longer needed when building.
• A Windows build has been added to CI.

[0.19.0]

• The Lua C library build now uses separate -sys crates, and bindgen rather than hand-maintained declarations. (Thanks @​pollend!) The "builtin-lua51" feature is now available.
• Value::Integer is now no longer available when building for Lua 5.1. (In Lua 5.1 there is no integer type).
• Add Function::dump() which produces the compiled version of a function (like the string.dump Lua function or lua_dump() C API).
• Add unsafe Chunk::into_function_allow_binary(). This allows loading a compiled binary generated from Function::dump().
• Add Initflags to control some settings done when Lua is initialised. They can be specified with the new unsafe Lua::unsafe_new_with_flags() constructor. The flags available (all set by default with the other constructors):
  • PCALL_WRAPPERS:
    • wrap pcall and xpcall so that they don't allow catching Rust panics
  • LOAD_WRAPPERS:
    • wrap functions load, loadfile, dofile (and loadstring for lua 5.1) to prevent loading compiled/bytecode modules.
  • REMOVE_LOADLIB:
    • Remove package.loadlib and the module finding functions which allow loading compiled C libraries.
• String<'lua> now implements Eq and Hash (can be useful for local collections within a context callback).

[0.18.0]

• Add support for multiple Lua versions, including 5.1, 5.3 and 5.4 (the default)
• Add implementations of FromLua and ToLua for [T;N].

[0.17.1]

• Add "lua-compat-mathlib" feature, which enables Lua's LUA_COMPAT_MATHLIB option.
• Bump num-traits version to 0.2.14 and fix some incompatibilities
• Fix some tests from improved diagnostics in recent rustc.

... (truncated)

Commits

• 262180f Merge pull request #257 from amethyst/fix-no-oslib
• fd0a24e Update for 0.19.4 release.
• 7ec47a3 Add CI testing for no-oslib.
• 5878315 Fix the sense of the cfg(feature = "lua-no-oslib") test.
• ffe8a41 Merge pull request #256 from amethyst/optional-oslib
• cb4f71d Fix Cargo.toml syntax issue.
• 9ffefa3 Update -sys crate versions.
• dea5602 Release prep.
• d213a74 Undo Cargo.toml hack.
• 6fc043a Add lua-no-oslib feature to other Lua versions.
• Additional commits viewable in compare view

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