patch 9.0.1782: prop_list() does not return text_padding_left

Problem:  prop_list() does not return text_padding_left
Solution: Store and return the text_padding_left value for text
          properties

closes: #12870

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

src/structs.h

@@ -827,6 +827,8 @@ typedef struct textprop_S
     int		tp_id;		// identifier
     int		tp_type;	// property type
     int		tp_flags;	// TP_FLAG_ values
+    int		tp_padleft;	// left padding between text line and virtual
+				// text
 } textprop_T;
 
 #define TP_FLAG_CONT_NEXT	0x1	// property continues in next line