users-guide 1.0.70 fails to install properly

[Dan Hensley <dan hensley att net>]

I just discovered a small problem with users-guide 1.0.70.  In the
Makefile, under install-data-local, the line
 for file in users-guide/figs/*.gif; do \
should read
 for file in users-guide/figs/*.png; do \

Otherwise, make install will fail.

Dan