Some fixes for FreeBSD

[thierry-FreeBSD]

OpenPBS does not compile "out of the box" on FreeBSD, and some files have to be patched:

• some headers are not available and configure fails;
• with_tcl and with_tk must be honored to detect TCL/TK;
• <sys/socket.h> must be included for qstat;
• the default PATH must include /usr/local/bin;
• systemd does not exist;
• recent clang fail on src/lib/Libtpp/tpp_platform.c.

[CLAassistant]

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