Call this function to set or remove a password character displayed in an edit control when the user types text.
When a password character is set, that character is displayed for each character the user types.
This member function has no effect on a multiple-line edit control.
When the SetPasswordChar member function is called, CEdit will redraw all visible characters using the character specified by ch.
If the edit control is created with the ES_PASSWORD style, the default password character is set to an asterisk (*). This style is removed if SetPasswordChar is called with ch set to 0.
For more information, see EM_SETPASSWORDCHAR in the Windows SDK.