Add MSRV policy

riscv-rt/.travis.yml

@@ -3,6 +3,7 @@ language: rust
 rust:
 - nightly
 - stable
+- 1.31.0 # MSRV
 
 env:
 - TARGET=x86_64-unknown-linux-gnu
@@ -15,6 +16,8 @@ matrix:
   exclude:
     - rust: stable
       env: TARGET=riscv64imac-unknown-none-elf
+    - rust: 1.31.0 # MSRV
+      env: TARGET=riscv64imac-unknown-none-elf
 
 
 before_install: set -e

riscv-rt/src/lib.rs

@@ -1,5 +1,12 @@
 //! Minimal startup / runtime for RISC-V CPU's
 //!
+//! # Minimum Supported Rust Version (MSRV)
+//!
+//! This crate is guaranteed to compile on stable Rust 1.31 and up. It *might*
+//! compile with older versions but that may change in any new patch release.
+//! Note that `riscv64imac-unknown-none-elf` and `riscv64gc-unknown-none-elf` targets
+//! are not supported on stable yet.
+//!
 //! # Features
 //!
 //! This crate provides