Special case printing -0

Use the 1/x trick to determine if a value is -0 and special case the
printing of it.

[closes #496]

lib/jasmine-core/jasmine.js

@@ -1354,6 +1354,8 @@ getJasmineRequireObj().pp = function(j$) {
         this.emitScalar('undefined');
       } else if (value === null) {
         this.emitScalar('null');
+      } else if (value === 0 && 1/value === -Infinity) {
+        this.emitScalar('-0');
       } else if (value === j$.getGlobal()) {
         this.emitScalar('<global>');
       } else if (value.jasmineToString) {

spec/core/PrettyPrintSpec.js

@@ -11,6 +11,7 @@ describe("j$.pp", function () {
     expect(j$.pp(jasmine.undefined)).toEqual("undefined");
     expect(j$.pp(3)).toEqual("3");
     expect(j$.pp(-3.14)).toEqual("-3.14");
+    expect(j$.pp(-0)).toEqual("-0");
   });
 
   it("should stringify arrays properly", function() {

src/core/PrettyPrinter.js

@@ -11,6 +11,8 @@ getJasmineRequireObj().pp = function(j$) {
         this.emitScalar('undefined');
       } else if (value === null) {
         this.emitScalar('null');
+      } else if (value === 0 && 1/value === -Infinity) {
+        this.emitScalar('-0');
       } else if (value === j$.getGlobal()) {
         this.emitScalar('<global>');
       } else if (value.jasmineToString) {