Fix some precision problems in Real.
Fix some precision problems in Real.

There still seem to be some problems lurking around the trig
methods, but at least these changes get Real able to pass
most of the tests we want it to pass. It's still in a "beta"
state (but the problems it has also exist in Haskell's CReal).

siddhartha-gadgil/spire,rklaehn/spire,tixxit/spire,codeaudit/spire,JackSullivan/spire,JackSullivan/spire,AlecZorab/spire,AlecZorab/spire,adampingel/spire,siddhartha-gadgil/spire,rklaehn/spire,guersam/spire,guersam/spire,woparry/spire,adampingel/spire,non/spire,codeaudit/spire,tixxit/spire,kevinmeredith/spire,woparry/spire,kevinmeredith/spire,non/spire