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.
diff --git a/src/ops.c b/src/ops.c
index 9af466b..1bc51d8 100644
--- a/src/ops.c
+++ b/src/ops.c
@@ -1091,14 +1091,14 @@
     yankreg_T	    *old_y_previous, *old_y_current;
     int		    retval;
 
-    if (Recording == FALSE)	    /* start recording */
+    if (reg_recording == 0)	    /* start recording */
     {
 	/* registers 0-9, a-z and " are allowed */
 	if (c < 0 || (!ASCII_ISALNUM(c) && c != '"'))
 	    retval = FAIL;
 	else
 	{
-	    Recording = c;
+	    reg_recording = c;
 	    showmode();
 	    regname = c;
 	    retval = OK;
@@ -1111,7 +1111,7 @@
 	 * needs to be removed again to put it in a register.  exec_reg then
 	 * adds the escaping back later.
 	 */
-	Recording = FALSE;
+	reg_recording = 0;
 	MSG("");
 	p = get_recorded();
 	if (p == NULL)
@@ -1318,7 +1318,7 @@
 								      == FAIL)
 		return FAIL;
 	}
-	Exec_reg = TRUE;	/* disable the 'q' command */
+	reg_executing = regname == 0 ? '"' : regname; // disable "q" command
     }
     return retval;
 }