Added precision parameter to wxString::From[C]Double().

Optionally support fixed precision in wxString::FromDouble() and FromCDouble()
methods. This is mostly useful for the latter to be able to format numbers in
portable way (using dot as decimal separator) without loss of precision but
also do it for the former for consistency.

Closes #12973.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67181 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/string.h

@@ -2326,12 +2326,12 @@ public:
       // convert to a double
   bool ToCDouble(double *val) const;
 
-  // create a string representing the given floating point number
+  // create a string representing the given floating point number with the
+  // default (like %g) or fixed (if precision >=0) precision
     // in the current locale
-  static wxString FromDouble(double val)
-    { return wxString::Format(wxS("%g"), val); }
+  static wxString FromDouble(double val, int precision = -1);
     // in C locale
-  static wxString FromCDouble(double val);
+  static wxString FromCDouble(double val, int precision = -1);
 
 #ifndef wxNEEDS_WXSTRING_PRINTF_MIXIN
   // formatted input/output