Update xterm to version 376 / rev 133 via SR 1036787
    
    https://build.opensuse.org/request/show/1036787
    by user msmeissn + dimstar_suse
    - update to 376:
      * modify configure script to always check for gcc attributes,
      * update install-sh.
      * fix parsing of result -u in vttests/halves.pl.
      * add a note in ctlseqs.ms about compatibility of TBC.
      * fix a copy/paste error in manual (patch by Grady Martin).
      * add  null-pointer checks in x_strcasecmp and x_strncasecmp, to help
        with error-recovery for a missing font (Debian #1022942). (forwarded request 1036713 from dirkmueller)