document MESA_TEX/TNL_PROG env vars
diff --git a/docs/envvars.html b/docs/envvars.html
index 6520bef..7b64dc9 100644
--- a/docs/envvars.html
+++ b/docs/envvars.html
@@ -20,6 +20,11 @@
If the value of MESA_DEBUG is "FP" floating point arithmetic errors will
generate exceptions.
<li>MESA_NO_DITHER - if set, disables dithering, overriding glEnable(GL_DITHER)
+<li>MESA_TEX_PROG - if set, implement conventional texture env modes with
+fragment programs (intended for developers only)
+<li>MESA_TNL_PROG - if set, implement conventional vertex transformation
+operations with vertex programs (intended for developers only).
+Setting this variable automatically sets the MESA_TEX_PROG variable as well.
</ul>
<p>