fail to link on ubuntu becouse of missing glXCreateGLXPixmap

[Sergey Litvinov]

geomview fails to link on Ubuntu 16.04. I got the following error message:

libtool: link: gcc -g -O2 -o .libs/gvx gvappear.o gvcameras.o gvcamui.o gvcolor.o gvcommands.o gvcredits.o gvevent.o gvfiles.o gvlights.o gvload.o gvmain.o gvmaterial.o gvmnpanel.o gvsave.o gvtoolui.o gvui.o buildinfo.o  ../common/libgvcommon.a ../../../../src/lib/mib/libmib.a -lXm -lXmu ../../../../src/lib/.libs/libgeomview.so -lSM -lICE -lXt -lXext -lX11 -lm -Wl,-rpath -Wl,/home/lisergey/prefix/geomview/lib
/usr/bin/ld: gvcamui.o: undefined reference to symbol 'glXCreateGLXPixmap'
//usr/lib/x86_64-linux-gnu/mesa/libGL.so.1: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
Makefile:504: recipe for target 'gvx' failed
make[1]: *** [gvx] Error 1
make[1]: Leaving directory '/home/lisergey/src/geomview/src/bin/geomview/x11'

I made this change

modified   src/bin/geomview/x11/Makefile.am
@@ -2,7 +2,7 @@ INCLUDES = $(default_includes) $(MOTIFINCLUDE) $(OPENGLINCLUDE) $(X_CFLAGS) -I..
 SUBDIRS = bitmaps interface

 gvx_LDADD = ../common/libgvcommon.a buildinfo.o \

- $(MOTIFUILIB) $(MOTIFLIBS) $(XMULIBS) $(OOGLLIB) $(XLIBS)
+ $(OPENGLLIBS) $(MOTIFUILIB) $(MOTIFLIBS) $(XMULIBS) $(OOGLLIB) $(XLIBS)
 gvx_DEPENDENCIES = ../common/libgvcommon.a buildinfo.o $(OOGLLIB)
 #gvx_LDFLAGS = -rpath $(libdir)

did autoreconf --install at it compiles.