web/links/index.htm: updated to Firefox bookmarks

lib/sh/util.sh: `set -o`: added pipefail option, to ensure that exit statuses (esp. for errexit) also work with pipelines (a|b)

lib/sh/util.sh: use new log+ with a numeric arg instead of multiple calls to log++

lib/sh/util.sh: use new log+ with a numeric arg instead of multiple calls to log++. use the command form of log-- (`log-- echo_func`) to counter the normal log++ performed by echo_func, for cases when the function name is descriptive and should be output at the same log_level as the commands it runs.

*{.sh,run}: removed extra space between function name and ()

lib/sh/util.sh: echo_func(): take the FUNCNAME as an argument (auto-added in the echo_func alias) instead of getting it from the FUNCNAME array (which would have produced an inaccurate value if another function call (such as log++) intervened between the caller and echo_func())

lib/sh/util.sh: echo_func(): display where the function was declared (using new func_loc()) instead of where echo_func() was called from. this is more intuitive when debugging, becaues the line # is where the function starts. it also helps remove the dependency on the FUNCNAME/BASH_* arrays, which would produce an inaccurate value if another function call (such as log++) intervened between the caller and echo_func().

lib/sh/util.sh: added func_loc(), which gets where a function was declared in the format file:line, and helper alias set_func_loc

lib/sh/util.sh: str2varname(): use bash's internal ${var//glob/repl} syntax, which supports character classes ([a-z], etc.), instead of sed (which is slower because it's an external command and uses regexps)

lib/sh/util.sh: added support for caching realpath() using the new shell-variable-based caching. this can be enabled via $realpath_cache and defaults to off because it's currently slower than without. note that the cache needs to be cleared in cd() because relative paths will become invalid.