#3 File -> Save after File -> Save As saves to original file

[ElLocoGato]

After a File -> Save As... operation, File -> Save saves to the original file instead of the new file.

Steps to Reproduce:
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- Open font1.pft
- File -> Save As... Save as font2.pft
- Make a modification
- File -> Save

Expected Results:
Modification should be saved to font2.pft

Actual Results:
Modification is saved to font1.pft

Perhaps CMainFrame::DoFileSaveAs() should update m_filename on successful save.