Allow macro-expanded macros in trailing expression positions to expand into statements:

```rust
macro_rules! m { () => { let x = 1; x } }
macro_rules! n { () => {
    m!() //< This can now expand into statements
}}
fn main() { n!(); }
```

and revert needless fallout fixes.

Author: jseyfried

src/libsyntax/parse/parser.rs

@@ -4066,7 +4066,8 @@ impl<'a> Parser<'a> {
     /// (or the lack thereof) -- c.f. `parse_stmt`.
     pub fn finish_parsing_statement(&mut self, mut stmt: Stmt) -> PResult<'a, Stmt> {
         if let StmtKind::Mac(mac) = stmt.node {
-            if mac.1 != MacStmtStyle::NoBraces || self.token == token::Semi {
+            if mac.1 != MacStmtStyle::NoBraces ||
+               self.token == token::Semi || self.token == token::Eof {
                 stmt.node = StmtKind::Mac(mac);
             } else {
                 let (mac, _style, attrs) = mac.unwrap();

src/test/run-pass/simd-intrinsic-generic-cast.rs

@@ -113,7 +113,7 @@ fn main() {
         // product macro
         ($from: ident $(, $from_: ident)*: $($to: ident),*) => {
             fn $from() { unsafe { $( test!($from, $to); )* } }
-            tests!($($from_),*: $($to),*);
+            tests!($($from_),*: $($to),*)
         };
         ($($types: ident),*) => {{
             tests!($($types),* : $($types),*);