merge: bugs-common

 * Set COLUMNS to MuttIndexWindow->cols in mutt_create_filter_fd. (closes #3837)
 * Fix infinite loop when help is bound to a named key combination.
 * Add real prototype for re_match_2_internal in regex.c
 * Clarify oppenc option documention. (closes #3846)
 * Include ncurses tinfo library if found.
 * Fix cppflags and muttlibs duplication with --with-gss.
 * Check $pgp_autoinline and $pgp_replyinline if oppenc is set. (closes #3846)

diff --cc configure.ac
Simple merge

diff --cc init.h
Simple merge

diff --cc keymap.c
Simple merge

diff --cc send.c
Simple merge