emacsclient.c: file name component fixes

* lib-src/emacsclient.c: Include <dosname.h>.
(file_name_absolute_p): Remove, as a code duplicate.
All uses replaced by IS_ABSOLUTE_FILE_NAME.
(set_local_socket): Don’t treat \ as a file name separator
on GNU and POSIX hosts.
1 job for master in 26 minutes and 14 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #98
test

00:26:14

 
Name Stage Failure
failed
test Test
make[2]: *** [check-doit] Error 1
Makefile:301: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/tzz/emacs/test'
Makefile:271: recipe for target 'check' failed
make[1]: *** [check] Error 2
make[1]: Leaving directory '/builds/tzz/emacs/test'
Makefile:955: recipe for target 'check' failed
make: *** [check] Error 2
ERROR: Job failed: exit code 1