merge: upstream changes

merge: upstream changes

 * Add mutt_buffer_mktemp() transition function
 * Add mutt_buffer_adv_mktemp() transition function
 * Always print mutt_buffer_pool_free() size debug output
 * add Buffer fixup functions
 * Remove conversion of nbsp to space
 * Ensure a resized empty buffer is null-terminated
 * Fix memleaks of saslconn on error paths
 * Fix memory leak on error in eat_regexp() and eat_date()
 * Document send-hooks are not executed for resumed messages
 * Fix a few memory leaks for idna conversion
 * Allow relative date hour/min/sec offsets
 * Add some brief documentation on OAUTH support
 * Update $index_format cross-references in manual
 * Add L10N comments to several unclear messages
 * Switch color chunk matching to use bsearch