fix missing parentheses around NaN/Infinity shorthands

[alexlamsl]

fixes #1724
fixes #1725

[kzc]

A couple of things:

• The tests should be using expect_exact.
• The uglified code is larger for NaN and 0/0 cases with this PR.

This PR:

$ echo 'var a = 0; console.log(++a % NaN | NaN ? a++ : 0);' | bin/uglifyjs -c
var a=0;console.log(++a%(0/0)|0/0?a++:0);

$ echo 'var a = 0; console.log(++a % (0/0) | (0/0) ? a++ : 0);' | bin/uglifyjs -c
var a=0;console.log(++a%(0/0)|0/0?a++:0);

v2.7.5:

$ echo 'var a = 0; console.log(++a % NaN | NaN ? a++ : 0);' | uglifyjs -c
var a=0;console.log(++a%NaN|NaN?a++:0);

$ echo 'var a = 0; console.log(++a % (0/0) | (0/0) ? a++ : 0);' | uglifyjs -c
var a=0;console.log(++a%NaN|NaN?a++:0);

[alexlamsl]

The tests should be using expect_exact

Good point - will update.

The uglified code is larger for NaN and 0/0 cases with this PR

See discussion on #1723 (comment)