`useMake` parsing not targets

[no1xsyzy]

The command make -prRn outputs include some 'targets' with a line of "# Not a target:" before, like the following:

# Not a target:
E01.md:
#  Implicit rule search has not been done.
#  Modification time never checked.
#  File has not been updated.

which should be filtered out.

Try take a look at these:
https://stackoverflow.com/a/26339924/6202760
https://github.com/GArik/bash-completion/blob/master/completions/make

[no1xsyzy]

It suddenly occurs to my mind that: what about add a setting to accept the output of make list or make _list to decide the targets?
This will also deal with #36