Fix premature truncation of brief descriptions in Doxygen comments.

Don't end the brief description at the first period if it's a period which is
part of "i.e." or "e.g.": escape the space following it to prevent Doxygen
from recognizing it as an end of sentence.

See #14866.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73084 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/unichar.h

@@ -54,7 +54,7 @@ public:
     value_type GetValue() const;
 
     /**
-        Returns true if the character is an ASCII character (i.e. if its value is less than 128).
+        Returns true if the character is an ASCII character (i.e.\ if its value is less than 128).
     */
     bool IsAscii() const;