Remove trailing semicolons from several macro definitions

[Aaron1011]

The x86 code contains several macros that following this pattern:

macro_rules! expr {
    () => { true; }
}

fn bar(_val: bool) {}

fn main() {
    bar(expr!());
}

Here, we have a macro expr! that expands to tokens sequence with
a trailing semicolon.

Currently, the trailing semicolon is ignored when the macro is invoked
in expression position, due to rust-lang/rust#33953
If this behavior is changed, then a large number of macro invocations in
stdarch will stop compiling.

Regardless of whether nor not this change is made, removing the
semicolon more clearly expresses the intent of the code - these macros
are designed to expand to the result of a function call, not ignore its
results (as the ; would suggest).

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Amanieu (or someone else) soon.

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