Testing: Add new tests, and new ways of testing, for floating-point.

- Adds a pragma to see binary output of double values (not portable)
- Print decimals that show more values, but in a portable way
  (lots of portability issues)
- Expand the tests to test more double values

Note: it is quite difficult to have 100% portable tests for floating point.
The current situation works by not printing full precision, and working around
several portability issues.

glslang/MachineIndependent/ParseHelper.cpp

@@ -269,7 +269,8 @@ void TParseContext::handlePragma(const TSourceLoc& loc, const TVector<TString>&
         intermediate.setUseStorageBuffer();
     } else if (tokens[0].compare("once") == 0) {
         warn(loc, "not implemented", "#pragma once", "");
-    }
+    } else if (tokens[0].compare("glslang_binary_double_output") == 0)
+        intermediate.setBinaryDoubleOutput();
 }
 
 //