Fix spelling errors and capitalization.

src/librustrt/args.rs

@@ -14,7 +14,7 @@
 //! the processes `argc` and `argv` arguments to be stored
 //! in a globally-accessible location for use by the `os` module.
 //!
-//! Only valid to call on linux. Mac and Windows use syscalls to
+//! Only valid to call on Linux. Mac and Windows use syscalls to
 //! discover the command line arguments.
 //!
 //! FIXME #7756: Would be nice for this to not exist.

src/librustrt/c_str.rs

@@ -19,7 +19,7 @@ string types are *not* null terminated.
 
 The other problem with translating Rust strings to C strings is that Rust
 strings can validly contain a null-byte in the middle of the string (0 is a
-valid unicode codepoint). This means that not all Rust strings can actually be
+valid Unicode codepoint). This means that not all Rust strings can actually be
 translated to C strings.
 
 # Creation of a C string

src/librustrt/local_ptr.rs

@@ -107,10 +107,10 @@ pub mod compiled {
     // efficient sequence of instructions. This also involves dealing with fun
     // stuff in object files and whatnot. Regardless, it turns out this causes
     // trouble with green threads and lots of optimizations turned on. The
-    // following case study was done on linux x86_64, but I would imagine that
+    // following case study was done on Linux x86_64, but I would imagine that
     // other platforms are similar.
     //
-    // On linux, the instruction sequence for loading the tls pointer global
+    // On Linux, the instruction sequence for loading the tls pointer global
     // looks like:
     //
     //      mov %fs:0x0, %rax