Fix font description for non-. decimal separators

Fix wxNativeFontInfo::ToString and FromString to work correctly under
locales that don't use '.' for decimal separator. The code incorrectly
parsed descriptions using ToCDouble and this '.', but wrote them out
using locale's native separator. Fixed by using FromCDouble for output
too.

src/common/fontcmn.cpp

@@ -812,9 +812,9 @@ wxString wxNativeFontInfo::ToString() const
 {
     wxString s;
 
-    s.Printf(wxT("%d;%f;%d;%d;%d;%d;%d;%s;%d"),
+    s.Printf(wxT("%d;%s;%d;%d;%d;%d;%d;%s;%d"),
              1,                                 // version
-             GetFractionalPointSize(),
+             wxString::FromCDouble(GetFractionalPointSize()),
              family,
              (int)style,
              weight,

src/msw/font.cpp

@@ -739,9 +739,9 @@ wxString wxNativeFontInfo::ToString() const
 {
     wxString s;
 
-    s.Printf(wxS("%d;%f;%ld;%ld;%ld;%ld;%ld;%d;%d;%d;%d;%d;%d;%d;%d;%s"),
+    s.Printf(wxS("%d;%s;%ld;%ld;%ld;%ld;%ld;%d;%d;%d;%d;%d;%d;%d;%d;%s"),
              1, // version
-             pointSize,
+             wxString::FromCDouble(pointSize),
              lf.lfHeight,
              lf.lfWidth,
              lf.lfEscapement,

src/osx/carbon/font.cpp

@@ -971,9 +971,9 @@ wxString wxNativeFontInfo::ToString() const
 {
     wxString s;
 
-    s.Printf(wxT("%d;%f;%d;%d;%d;%d;%d;%s;%d"),
+    s.Printf(wxT("%d;%s;%d;%d;%d;%d;%d;%s;%d"),
         1, // version
-        GetFractionalPointSize(),
+        wxString::FromCDouble(GetFractionalPointSize()),
         GetFamily(),
         (int)GetStyle(),
         GetNumericWeight(),