Working from up-to-date pkgsrc, I'm unable to build xbattbar on 1.6.1:

gcc -O2      -I/usr/X11R6/include    -DCSRG_BASED  -DFUNCPROTO=15 -DNARROWPROTO       -I/usr/pkg/include -I/usr/X11R6/include -c xbattbar.c
xbattbar.c: In function `battery_check':
xbattbar.c:664: `_PATH_SYSMON' undeclared (first use in this function)
xbattbar.c:664: (Each undeclared identifier is reported only once
xbattbar.c:664: for each function it appears in.)
xbattbar.c:715: `ENVSYS_INDICATOR' undeclared (first use in this function)
*** Error code 1

Stop.
make: stopped in /usr/pkgsrc/sysutils/xbattbar/work/xbattbar-1.4.2
*** Error code 1

Stop.
make: stopped in /usr/pkgsrc/sysutils/xbattbar
*** Error code 1

Stop.
make: stopped in /usr/pkgsrc/sysutils/xbattbar


		--Steve Bellovin, http://www.research.att.com/~smb