For a cursor that is a reference, retrieve a cursor representing the
entity that it references.
Reference cursors refer to other entities in the AST. For example, an
Objective-C superclass reference cursor refers to an Objective-C class.
This function produces the cursor for the Objective-C class from the
cursor for the superclass reference. If the input cursor is a
declaration or definition, it returns that declaration or definition
unchanged. Otherwise, returns the NULL cursor.
For a cursor that is a reference, retrieve a cursor representing the entity that it references.
Reference cursors refer to other entities in the AST. For example, an Objective-C superclass reference cursor refers to an Objective-C class. This function produces the cursor for the Objective-C class from the cursor for the superclass reference. If the input cursor is a declaration or definition, it returns that declaration or definition unchanged. Otherwise, returns the NULL cursor.