patch 8.0.1505: debugger can't break on a condition

Problem:    Debugger can't break on a condition. (Charles Campbell)
Solution:   Add ":breakadd expr". (Christian Brabandt, closes #859)

src/structs.h

@@ -3262,6 +3262,22 @@ typedef struct {
   char_u   buffer[64];
 } context_sha256_T;
 
+/*
+ * types for expressions.
+ */
+typedef enum
+{
+    TYPE_UNKNOWN = 0
+    , TYPE_EQUAL	/* == */
+    , TYPE_NEQUAL	/* != */
+    , TYPE_GREATER	/* >  */
+    , TYPE_GEQUAL	/* >= */
+    , TYPE_SMALLER	/* <  */
+    , TYPE_SEQUAL	/* <= */
+    , TYPE_MATCH	/* =~ */
+    , TYPE_NOMATCH	/* !~ */
+} exptype_T;
+
 /*
  * Structure used for reading in json_decode().
  */