*{.sh,run}: use standard WARNING syntax for warning labels

fix: lib/sh/util.sh: verbosity_compat(): documented that this should not be run until right before executing an external command, so that it doesn't mess up the logging mechanism

bugfix: bin/make: don't run verbosity_compat until right before executing the external command, so that it doesn't mess up the logging mechanism. this is run automatically by command(), so there is no need to do anything here. note that logging bugs like these can now be troubleshooted much more easily with pst() to narrow down which functions could be causing the problem.

bugfix: lib/sh/util.sh: functions called by pst(): commented out/removed logging calls that would have caused infinite recursion when pst()'ing a logging function

lib/sh/util.sh: echo_func(): get call context before wrapper(s), which is more useful for debugging. this uses skip_stack_frames()'s lookahead=1 mode.

fix: lib/sh/util.sh: skip_stack_frames() callers: updated for new skip_stack_frames rather than get_stack_frame behavior

lib/sh/util.sh: skip_stack_frames(): added lookahead support, which looks at entry after current to deterine whether to skip current. this is useful for skipping wrappers, by looking at the calling function's name.

fix: lib/sh/util.sh: skip_stack_frames(): for new skip_stack_frames rather than get_stack_frame behavior, stack frames must be skipped in the caller to preserve the stack frame pointer

lib/sh/util.sh: get_stack_frame_after(): renamed to skip_stack_frames() for clarity

lib/sh/util.sh: added skip_stack_frame_in_caller, unskip_stack_frame_in_caller