Add JSON logging; Improvements and Fixes

• Check for duplicate pipe definition
  pipe endpoints can only be used once. If two times the same source or sink were specified in the command line, the behavior was (and still is) undefined.
  Now a check was added that emits a error log, if a pipe endpoint is specified twice.
• Added json logging
  Using the -j option pipexec now logs in json format that can be parsed. This provides information about status and exit codes of child processes.
• Exit with 1 when one child fails
  When at least one child fails, pipexec also fails with '1'.
• Check for rubbish on the command line
  Additional or unparsable command line arguments are now seen as an error. Before there were silently ignored.
• Fixed false positive dangling pointer check of gcc 12
  GCC introduces a new dangling pointer check which runs into a false positive.
• Add compile check for wide range of compilers
  As public travis access was switched off some time, pipexec now uses github CI/CD for compile check. The following compilers are checked:
  • gcc: 9, 10, 11, 12
  • clang: 10, 11, 12, 13, 14