ENH: add syncState() method to serial streams (#2623)

- in places where direct reading from the std::stream is used,
  this method can be used to ensure that the OpenFOAM Sstream state
  is properly updated from the std::stream.

ENH: restrict stream renaming to ISstream

- non-const access was previously declared at the top-level (IOstream)
  but that not only added in potentially odd setting of the static
  fileName, but also meant that the OFstream name() could potentially
  be altered after opening a file and thus be inconsistent with the
  underlying file that had been opened.

  Now restrict name modification to ISstream (and ITstream
  counterpart). Does not affect any existing valid code.

STYLE: non-default OFstream destructor (for future file staging)

src/fileFormats/ensight/file/ensightFile.C

@@ -149,6 +149,7 @@ Foam::Ostream& Foam::ensightFile::writeString(const char* str)
     {
         buf[79] = 0;  // max 79 in ASCII, ensure it is indeed nul-terminated
         stdStream() << buf;
+        syncState();
     }
 
     return *this;
@@ -186,6 +187,7 @@ Foam::Ostream& Foam::ensightFile::write
 )
 {
     stdStream().write(buf, count);
+    syncState();
     return *this;
 }
 
@@ -204,6 +206,7 @@ Foam::Ostream& Foam::ensightFile::write(const int32_t val)
     {
         stdStream().width(10);
         stdStream() << val;
+        syncState();
     }
 
     return *this;
@@ -232,6 +235,7 @@ Foam::Ostream& Foam::ensightFile::write(const float val)
     {
         stdStream().width(12);
         stdStream() << val;
+        syncState();
     }
 
     return *this;
@@ -260,6 +264,7 @@ Foam::Ostream& Foam::ensightFile::write
     {
         stdStream().width(fieldWidth);
         stdStream() << value;
+        syncState();
     }
 
     return *this;
@@ -271,6 +276,7 @@ void Foam::ensightFile::newline()
     if (format() == IOstreamOption::ASCII)
     {
         stdStream() << nl;
+        syncState();
     }
 }