Restructured library documentation
diff --git a/Doc/lib/libsgi.tex b/Doc/lib/libsgi.tex
new file mode 100644
index 0000000..f8c87b0
--- /dev/null
+++ b/Doc/lib/libsgi.tex
@@ -0,0 +1,4 @@
+\chapter{SGI IRIX ONLY}
+
+The modules described in this chapter provide interfaces to features
+that are unique to SGI's IRIX operating system (versions 4 and 5).