Help: Add cross-references for CMAKE_CURRENT_FUNCTION* docs

Help/variable/CMAKE_CURRENT_FUNCTION.rst

@@ -4,3 +4,7 @@ CMAKE_CURRENT_FUNCTION
 When executing code inside a :command:`function`, this variable
 contains the name of the current function.  It can be useful for
 diagnostic or debug messages.
+
+See also :variable:`CMAKE_CURRENT_FUNCTION_LIST_DIR`,
+:variable:`CMAKE_CURRENT_FUNCTION_LIST_FILE` and
+:variable:`CMAKE_CURRENT_FUNCTION_LIST_LINE`.

Help/variable/CMAKE_CURRENT_FUNCTION_LIST_FILE.rst

@@ -3,3 +3,7 @@ CMAKE_CURRENT_FUNCTION_LIST_FILE
 
 When executing code inside a :command:`function`, this variable
 contains the full path to the listfile that defined the current function.
+
+See also :variable:`CMAKE_CURRENT_FUNCTION`,
+:variable:`CMAKE_CURRENT_FUNCTION_LIST_DIR` and
+:variable:`CMAKE_CURRENT_FUNCTION_LIST_LINE`.

Help/variable/CMAKE_CURRENT_FUNCTION_LIST_LINE.rst

@@ -4,3 +4,7 @@ CMAKE_CURRENT_FUNCTION_LIST_LINE
 When executing code inside a :command:`function`, this variable
 contains the line number in the listfile where the current function
 was defined.
+
+See also :variable:`CMAKE_CURRENT_FUNCTION`,
+:variable:`CMAKE_CURRENT_FUNCTION_LIST_DIR` and
+:variable:`CMAKE_CURRENT_FUNCTION_LIST_FILE`.