[Chapel Merge] Fix problem where 'make docs' would run sphinx twi

Branch: refs/heads/master
Revision: 0f3fd84
Author: mppf
Log Message:

Merge pull request #16869 from mppf/fix-man-chapel

Fix problem where ‘make docs’ would run sphinx twice

Follow-up to PR #16864.

PR #16864 added an invocation of the Makefile target man-chapel but
that was wrong. make man-chapel creates a single man page with all the
API docs (in man/man3/chapel.1). I meant to make man/man1/chpl.1. This PR
fixes it by adding man-chpl to be symmetrical with man-chpldoc which
just creates the man page for the command and then updates make docs to
run that. While there, it makes sure that these targets have the chpldoc
dependencies.

Reviewed by @ben-albrecht - thanks!

Modified Files:
M Makefile.devel

Compare: https://github.com/chapel-lang/chapel/compare/2fb207f8fdf9...0f3fd847f837