lib/util/stdstr: pass *argv to sed/cut/...
lib/atexit: set ATEXIT_ENABLED=y,n
lib/atexit: dont append whitespace to __ATEXIT_FUNCTIONS
lib/fs/lockfile: control atexit behavior

lockfile now registers only one atexit function which then
releases all known locks iff ATEXIT_RELEASE_AT_EXIT is set to 'y'.
lib/itertools: fix ITER_SKIP_COMMENT
make_scripts.sh: add tmp/ dir to non-flat scripts
CC: bypass system shlibcc via SYSTEM_SHLIBCC=n
script generation: use shlibcc's stable sorting