patch 8.1.0020: cannot tell whether a register is executing or recording

Problem:    Cannot tell whether a register is being used for executing or
            recording.
Solution:   Add reg_executing() and reg_recording(). (Hirohito Higashi,
            closes #2745)  Rename the global variables for consistency.  Store
            the register name in reg_executing.

runtime/doc/eval.txt

@@ -2302,6 +2302,8 @@ range({expr} [, {max} [, {stride}]])
 				List	items from {expr} to {max}
 readfile({fname} [, {binary} [, {max}]])
 				List	get list of lines from file {fname}
+reg_executing()			Number	get the executing register name
+reg_recording()			String	get the recording register name
 reltime([{start} [, {end}]])	List	get time value
 reltimefloat({time})		Float	turn the time value into a Float
 reltimestr({time})		String	turn time value into a String
@@ -6558,6 +6560,15 @@ readfile({fname} [, {binary} [, {max}]])
 		the result is an empty list.
 		Also see |writefile()|.
 
+reg_executing()						*reg_executing()*
+		Returns the single letter name of the register being executed.
+		Returns an empty string when no register is being executed.
+		See |@|.
+
+reg_recording()						*reg_recording()*
+		Returns the single letter name of the register being recorded.
+		Returns an empty string string when not recording.  See |q|.
+
 reltime([{start} [, {end}]])				*reltime()*
 		Return an item that represents a time value.  The format of
 		the item depends on the system.  It can be passed to

runtime/doc/usr_41.txt

@@ -1018,6 +1018,8 @@ Various:					*various-functions*
 	getreg()		get contents of a register
 	getregtype()		get type of a register
 	setreg()		set contents and type of a register
+	reg_executing()		return the name of the register being executed
+	reg_recording()		return the name of the register being recorded
 
 	shiftwidth()		effective value of 'shiftwidth'