Add flag values in WAL description to all heap records

Fix incorrect routine name in xlog_heapam.h

Improve docs for the new INCLUDE directive in CREATE/ALTER TABLE.

Un-break contrib install with llvm.

Minor cleanups for install_llvm_module/uninstall_llvm_module Make macros.

Add missing and dangling downlink checks to amcheck

Fix wrong validation of top-parent pointer during page deletion in Btree.

Fix a few typos in comments and variable names.