dselect: Implement delete operator with size argument

The C++14 spec states that if the delete operator is defined then the
one with a size argument must also be implemented.

Warned-by: gcc-6

debian/changelog

@@ -4,6 +4,8 @@ dpkg (1.18.5) UNRELEASED; urgency=medium
     This affects «dpkg-deb -z». Closes: #809174
   * Do not abort when traversing symlinks to directories in dpkg-scanpackages
     and dpkg-scansources. Closes: #809219
+  * Implement delete operator with size argument in dselect, required by the
+    C++14 spec when the size-less delete operator is defined.
   * Documentation:
     - Say value instead of option in deb-control(5).
     - Mark debian changelog format in bold in dpkg-parsechangelog(1).

dselect/main.cc

@@ -369,6 +369,12 @@ operator delete(void *p) DPKG_ATTR_NOEXCEPT
   free(p);
 }
 
+extern void
+operator delete(void *p, size_t size) DPKG_ATTR_NOEXCEPT
+{
+  free(p);
+}
+
 urqresult urq_list(void) {
   modstatdb_open((modstatdb_rw)(msdbrw_writeifposs |
                                 msdbrw_available_readonly));