Merge branch 'refs/heads/t/lopsub'

Conversion to lopsub and a few other improvements on top of it.

* refs/heads/t/lopsub:
  INSTALL: Explain how to use CPPFLAGS and LDFLAGS.
  build: Introduce DSS_CPPFLAGS.
  build: Fix cc command which creates dependencies,
  build: Combine CFLAGS and DEBUG_CFLAGS.
  Implement --checksum.
  run: Improve error diagnostics for chdir(2) failure.
  run: Improve error message if dss is already running.
  run: Fix exit status in case another dss process is running.
  build: Add target install and install-strip.
  Convert dss to lopsub.
  Remove --no-resume.

diff --cc NEWS
index c87e411dfd311f9cc1ae0f9697581e58855c37d4,15323207ace195048ca7ee69de66e22f2969ea7c..755cad21834cc7b6d150746e6555544d706802c6
--- 1/NEWS
--- 2/NEWS
+++ b/NEWS
@@@ -1,9 -1,3 +1,26 @@@
 +-----------------------
 +x.y.z (to be announced)
 +-----------------------
 +
 + - Improved error diagnostics for the kill subcommand.
 +
++ - The --no-resume option has been removed.
++
++ - The gengetopt option parser has been replaced by the
++ [lopsub](http://people.tuebingen.mpg.de/~maan/lopsub) library. Hence
++ lopsub must be installed to compile this package. Also help2man is
++ no longer required since lopsub has built-in roff support.
++
++ - "make install" will install the executable and the man page.
++
++ - In run mode, dss no longer exits successfully if another instance
++ is already running.
++
++ - New option --checksum to let rsync compute checksums occasionally.
++
++ - CFLAGS, CPPFLAGS and LDFLAGS can now be used to override the flags
++ of the build system.
++
  ------------------
  0.1.7 (2017-04-17)
  ------------------