patch 8.1.2371: FEAT_TEXT_PROP is a confusing name

Problem:    FEAT_TEXT_PROP is a confusing name.
Solution:   Use FEAT_PROP_POPUP. (Naruhiko Nishino, closes #5291)
diff --git a/src/vim.h b/src/vim.h
index b7f7387..19c19de 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -653,7 +653,7 @@
 #define POPUP_HANDLED_4	    0x08    // used by may_update_popup_mask()
 #define POPUP_HANDLED_5	    0x10    // used by update_popups()
 
-#ifdef FEAT_TEXT_PROP
+#ifdef FEAT_PROP_POPUP
 # define WIN_IS_POPUP(wp) ((wp)->w_popup_flags != 0)
 #else
 # define WIN_IS_POPUP(wp) 0
@@ -2072,7 +2072,7 @@
     short_u	origin_end_col;
     short_u	word_start_col;
     short_u	word_end_col;
-#ifdef FEAT_TEXT_PROP
+#ifdef FEAT_PROP_POPUP
     // limits for selection inside a popup window
     short_u	min_col;
     short_u	max_col;