parse error mixin #628

Mixin allows for any placeholder css rules.

.placeholder(@rules) {

    &::-webkit-input-placeholder {
        @rules();
    }
    &:-moz-placeholder {
        @rules();
    }
    &::-moz-placeholder {
        @rules();
    }
    &:-ms-input-placeholder {
        @rules();
    }
}
Example usage:

.placeholder({
    color: #0000FF;
    text-transform: uppercase;
});