patch 8.2.2295: incsearch does not detect empty pattern properly

Problem:    Incsearch does not detect empty pattern properly.
Solution:   Return magic state when skipping over a pattern. (Christian
            Brabandt, closes #7612, closes #6420)

src/structs.h

@@ -4321,8 +4321,20 @@ typedef struct
 // with iconv() to be able to allocate a buffer.
 #define ICONV_MULT 8
 
+// Used for "magic_overruled".
 typedef enum {
-    MAGIC_NOT_SET,	// p_magic not overruled
-    MAGIC_ON,		// magic on inside regexp
-    MAGIC_OFF		// magic off inside regexp
+    OPTION_MAGIC_NOT_SET,	// p_magic not overruled
+    OPTION_MAGIC_ON,		// magic on inside regexp
+    OPTION_MAGIC_OFF		// magic off inside regexp
+} optmagic_T;
+
+// Magicness of a pattern, used by regexp code.
+// The order and values matter:
+//  magic <= MAGIC_OFF includes MAGIC_NONE
+//  magic >= MAGIC_ON  includes MAGIC_ALL
+typedef enum {
+    MAGIC_NONE = 1,		// "\V" very unmagic
+    MAGIC_OFF = 2,		// "\M" or 'magic' off
+    MAGIC_ON = 3,		// "\m" or 'magic'
+    MAGIC_ALL = 4		// "\v" very magic
 } magic_T;