updated manual

doc/rust.md

@@ -573,8 +573,7 @@ The top level of this tree is a module that is anonymous (from the point of view
 
 The Rust compiler is always invoked with a single source file as input, and always produces a single output crate.
 The processing of that source file may result in other source files being loaded as modules.
-Source files typically have the extension `.rs` but, by convention,
-source files that represent crates have the extension `.rc`, called *crate files*.
+Source files have the extension `.rs`.
 
 A Rust source file describes a module, the name and
 location of which -- in the module tree of the current crate -- are defined
@@ -3286,7 +3285,7 @@ As an example, to see all the logs generated by the compiler, you would set
 you would set it to `rustc::metadata::creader`. To see just error logging
 use `rustc=0`.
 
-Note that when compiling either `.rs` or `.rc` files that don't specify a
+Note that when compiling source files that don't specify a
 crate name the crate is given a default name that matches the source file,
 with the extension removed. In that case, to turn on logging for a program
 compiled from, e.g. `helloworld.rs`, `RUST_LOG` should be set to `helloworld`.