Errors building GNGEO makefile

[devillion]

I get this error when trying to build the makefile for GNGEO on my X11 machine.

<blockquote>
In file included from opengl.c:11:
glproc.h:7: parse error before `red'
glproc.h:8: parse error before `mask'
glproc.h:10: parse error before `cap'
glproc.h:11: parse error before `GLsizei'
glproc.h:12: parse error before `target'
glproc.h:13: parse error before `pname'
glproc.h:14: parse error before `target'
glproc.h:15: parse error before `mode'
glproc.h:17: parse error before `s'
glproc.h:18: parse error before `s'
opengl.c: In function `blitter_opengl_init':
opengl.c:92: `GL_COLOR_BUFFER_BIT' undeclared (first use in this function)
opengl.c:92: (Each undeclared identifier is reported only once
opengl.c:92: for each function it appears in.)
opengl.c:94: `GL_TEXTURE_2D' undeclared (first use in this function)
opengl.c:99: `GL_TEXTURE_MAG_FILTER' undeclared (first use in this function)
opengl.c:99: `GL_LINEAR' undeclared (first use in this function)
opengl.c:100: `GL_TEXTURE_MIN_FILTER' undeclared (first use in this function)
opengl.c:106: `GL_TEXTURE_WRAP_S' undeclared (first use in this function)
opengl.c:106: `GL_CLAMP' undeclared (first use in this function)
opengl.c:107: `GL_TEXTURE_WRAP_T' undeclared (first use in this function)
opengl.c:120: `GL_UNPACK_ROW_LENGTH' undeclared (first use in this function)
opengl.c: In function `blitter_opengl_resize':
opengl.c:148: `GL_TEXTURE_2D' undeclared (first use in this function)
opengl.c: In function `blitter_opengl_update':
opengl.c:164: `GL_TEXTURE_2D' undeclared (first use in this function)
opengl.c:164: `GL_RGB' undeclared (first use in this function)
opengl.c:165: `GL_QUADS' undeclared (first use in this function)
make[3]: *** [opengl.o] Error 1
make[3]: Leaving directory `/home/mike/gngeo-0.6.1/src/blitter'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/home/mike/gngeo-0.6.1/src'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/mike/gngeo-0.6.1'
make: *** [all-recursive-am] Error 2</blockquote>

What is wrong?