/Makefile: new config target (part of install): install our bin/make in the user's ~/bin dir so that bin/make (with filtering of verbose messages) will always be used instead of standard make (without us needing to change every occurrence of make to bin/make!)

bugfix: bin/make: use standard make logging port (1) instead of $log_fd (30) so that the output of bin/make can in turn be filtered by util.sh using the standard cmd_log_fd=1

lib/sh/util.sh: command(): print the log_fd in effect in case the user changes it

lib/sh/make.sh: make(): log the messages about making included Makefiles at log_level 4 instead of 3, so that verbosity 3 can be used to see the vars being used by the filtering process (i.e. the filtering process must still be enabled at verbosity 3)

bin/make: use `readlink -f` on BASH_SOURCE⁰ so that this script can also be run via a symlink

lib/sh/util.sh: no_PATH_recursion(): also remove $top_symlink_dir_abs

lib/sh/util.sh: added $top_symlink_dir_abs

lib/sh/util.sh: $top_dir_orig: renamed to $top_symlink_dir since this reflects better what the dir actually represents, and when it differs from $top_dir

lib/sh/make.sh: make(): fixed func name in usage

bin/make: don't print make cmd by default, so that only `make` output is printed at verbosity 1