0029399: Optimize reading of floating point values from text strings

Function Strtod() is reimplemented using open source (MIT-style license) code by David M. Gay instead of strtod() provided by standard run-time library. This improves its performance by 3-10 times.

Functions Atof(), Strtod(), Printf(), Sprintf(), Fprintf() are declared as extern "C" to be usable from C programs.

Strtod() is used in Interface_FileReaderData::Fastof() and in RWStl_Reader to accelerate their work.

DRAW command QATestAtof and test perf fclasses strtod are added to check correctness and performance of Strtod().
Test perf draw restore is added to monitor performance of reading BREP files.

Minor off-topic corrections:
- method Standard_GUID::Assign (const Standard_UUID&) is implemented (was empty);
- Precision.hxx is included in BRepMesh_Vertex.hxx that uses it.

src/BRepMesh/BRepMesh_Vertex.hxx

@@ -15,11 +15,9 @@
 #ifndef _BRepMesh_Vertex_HeaderFile
 #define _BRepMesh_Vertex_HeaderFile
 
-#include <Standard.hxx>
-#include <Standard_DefineAlloc.hxx>
-#include <Standard_Macro.hxx>
-#include <gp_XY.hxx>
 #include <BRepMesh_DegreeOfFreedom.hxx>
+#include <gp_XY.hxx>
+#include <Precision.hxx>
 
 //! Light weighted structure representing vertex 
 //! of the mesh in parametric space. Vertex could be