Allow deleting a record at database creation.

Using a magical record type "#" will allow the user to
delete previously created record  from the database.

documentation/RELEASE_NOTES.md

@@ -22,6 +22,21 @@ should also be read to understand what has changed since earlier releases:
 
 ## Changes made on the 7.0 branch since 7.0.8.1
 
+### Allow users to delete previously created records from the database
+
+From this release, record instances and aliases that have already been loaded
+by an IOC can be removed from the database again before the call to iocInit
+by loading a second instance of the named records but using `"#"` in place of
+the record type. Values for the fields are not required or advised, just use
+an empty record body { }. This is useful when a template defines records that
+are not wanted in some IOCs, without having to split or duplicate the original
+template.
+
+For example this will remove the record named "unwanted":
+
+```
+record("#", "unwanted") { }
+```
 
 -----
 

modules/database/src/ioc/dbStatic/dbLexRoutines.c

@@ -1119,6 +1119,19 @@ static void dbRecordHead(char *recordType, char *name, int visible)
         return;
     }
 
+    if (recordType[0] == '#' && recordType[1] == 0) {
+        status = dbFindRecord(pdbentry, name);
+        if (status == 0) {
+            dbDeleteRecord(pdbentry);
+            fprintf(stderr, ERL_WARNING ": Record \"%s\" DELETED!\n", name);
+            return; /* done */
+        }
+        fprintf(stderr, ERL_ERROR ": Record \"%s\" not found\n", name);
+        yyerror(NULL);
+        duplicate = TRUE;
+        return;
+    }
+
     status = dbFindRecordType(pdbentry, recordType);
     if (status) {
         fprintf(stderr, "Record \"%s\" is of unknown type \"%s\"\n",