Teach find_library and find_package to search lib32 paths (#11260)

Add a ``FIND_LIBRARY_USE_LIB32_PATHS`` global property analogous to the
``FIND_LIBRARY_USE_LIB64_PATHS`` property.  This helps find commands on
multilib systems that use ``lib32`` directories and either do not have
``lib`` symlinks or point ``lib`` to ``lib64``.

Source/cmFindPackageCommand.h

@@ -148,6 +148,7 @@ private:
   bool NoUserRegistry;
   bool NoSystemRegistry;
   bool DebugMode;
+  bool UseLib32Paths;
   bool UseLib64Paths;
   bool PolicyScope;
   std::string LibraryArchitecture;