merge: small fixes and tidying

 * clang-format
 * use enum return value
 * test: fix lcov out-of-tree build
 * test: boolify test_mutt_pattern_comp()
 * refactor: replace ctime() with strftime()
 * bug: prevent unterminated string
 * check range of uuencoded char
 * log failed atoi() calls
 * fix buffer handling
 * restore randomness to mutt_buffer_mktemp_full()
 * check state buffer
 * check for overflow in mutt_edit_content_type()
 * reduce scope of variables
 * add/remove checks
 * use param, not global, in prereq()
 * add brackets to clarify logic
 * misc small changes