Switch to Rust 1.31 as minimum supported version

Too many dependencies switched and we can't really keep everything at an
older version.

Commented out for now until stable becomes 1.32.

.gitlab-ci.yml

@@ -48,10 +48,10 @@ stages:
     - cargo build --color=always --all --all-features
     - G_DEBUG=fatal_warnings cargo test --color=always --all --all-features
 
-test 1.28:
-  # 1.28 img
+.test 1.31:
+  # 1.31 img
   # https://hub.docker.com/_/rust/
-  image: "rust:1.28-slim"
+  image: "rust:1.31-slim"
   <<: *cargo_test
 
 test stable:

examples/Cargo.toml

@@ -29,11 +29,6 @@ pangocairo = { git = "https://github.com/gtk-rs/pangocairo", optional = true }
 # Using my personal repository (vjaquez) for glutin until
 # https://github.com/tomaka/glutin/pull/1082 is merged
 glutin = { git = "https://github.com/ceyusa/glutin", branch="native-display", optional = true }
-# Newer versions do not compile with rustc 1.28 so pin it for the time being
-# This dependency comes from backtrace, which comes from failure
-rustc-demangle = "0.1.10"
-# This dependency comes from glutin and winit, which comes from failure
-stb_truetype = { version = "= 0.2.4", optional = true }
 
 [build-dependencies]
 gl_generator = { version = "0.9", optional = true }

tutorials/Cargo.toml

@@ -14,9 +14,6 @@ gstreamer-app = { path = "../gstreamer-app" }
 gstreamer-pbutils = { path = "../gstreamer-pbutils" }
 byte-slice-cast = "0.2"
 failure = "0.1.0"
-# Newer versions do not compile with rustc 1.28 so pin it for the time being
-# This dependency comes from backtrace, which comes from failure
-rustc-demangle = "0.1.10"
 
 [features]
 tutorial5 = ["gtk", "gdk"]