string: Added const replace and replaceAll

which return the replaced string rather than modify the string the function is
called for.

src/OpenFOAM/primitives/strings/string/string.C

@@ -78,6 +78,17 @@ Foam::string& Foam::string::replace
 }
 
 
+Foam::string Foam::string::replace
+(
+    const string& oldStr,
+    const string& newStr,
+    size_type start
+) const
+{
+    return string(*this).replace(oldStr, newStr, start);
+}
+
+
 Foam::string& Foam::string::replaceAll
 (
     const string& oldStr,
@@ -100,6 +111,17 @@ Foam::string& Foam::string::replaceAll
 }
 
 
+Foam::string Foam::string::replaceAll
+(
+    const string& oldStr,
+    const string& newStr,
+    size_type start
+) const
+{
+    return string(*this).replaceAll(oldStr, newStr, start);
+}
+
+
 Foam::string& Foam::string::expand(const bool allowEmpty)
 {
     stringOps::inplaceExpand(*this, allowEmpty);