HP's tablet ship may have sailed, but at least you can still count on the outfit for your next reverse Polish notation calculator. That's right, HP's 12c just hit the big three-oh. The classic calculator is celebrating its mid life crisis 30th year in production with a special limited edition number cruncher, featuring an etched faceplate declaring its pedigree. If 1981's coolest calculator isn't your style, don't fret -- HP is also releasing a limited edition run of 1982's HP 15c, boasting a hundred-fold improvement in performance over its predec