C++: Remove unused external_package tables from the dbscheme

cpp/ql/lib/semmlecode.cpp.dbscheme

@@ -217,29 +217,6 @@ diagnostics(
 
 /*- C++ dbscheme -*/
 
-/**
- * Information about packages that provide code used during compilation.
- * The `id` is just a unique identifier.
- * The `namespace` is typically the name of the package manager that
- * provided the package (e.g. "dpkg" or "yum").
- * The `package_name` is the name of the package, and `version` is its
- * version (as a string).
- */
-external_packages(
-    unique int id: @external_package,
-    string namespace : string ref,
-    string package_name : string ref,
-    string version : string ref
-);
-
-/**
- * Holds if File `fileid` was provided by package `package`.
- */
-header_to_external_package(
-    int fileid : @file ref,
-    int package : @external_package ref
-);
-
 /*
  * C++ dbscheme
  */

cpp/ql/src/Metrics/Dependencies/ExternalDependencies.qll

@@ -26,12 +26,6 @@ private newtype LibraryT =
   LibraryTElement(LibraryElement lib, string name, string version) {
     lib.getName() = name and
     lib.getVersion() = version
-  } or
-  LibraryTExternalPackage(@external_package ep, string name, string version) {
-    exists(string package_name |
-      external_packages(ep, _, package_name, version) and
-      name = package_name
-    )
   }
 
 /**
@@ -41,10 +35,7 @@ class Library extends LibraryT {
   string name;
   string version;
 
-  Library() {
-    this = LibraryTElement(_, name, version) or
-    this = LibraryTExternalPackage(_, name, version)
-  }
+  Library() { this = LibraryTElement(_, name, version) }
 
   string getName() { result = name }
 
@@ -63,11 +54,6 @@ class Library extends LibraryT {
       this = LibraryTElement(lib, _, _) and
       result = lib.getAFile()
     )
-    or
-    exists(@external_package ep |
-      this = LibraryTExternalPackage(ep, _, _) and
-      header_to_external_package(unresolveElement(result), ep)
-    )
   }
 }