Added a purpose comment for ioctl_fix_ctrl

From-SVN: r27455

gcc/ChangeLog

@@ -13,6 +13,7 @@ Wed Jun  9 06:50 1999  Bruce Korb <ddsinc09@ix.netcom.com>
 
 	*fixinc/inclhack.def(sun_auth_proto): bypass the patch if
 	the typed arguments are not part of a comment
+	(ioctl_fix_ctrl): Added a purpose comment
 	*fixinc/fixincl.x: regenerate
 	*fixinc/inclhack.sh: regenerate
 

gcc/fixinc/inclhack.def

@@ -587,6 +587,16 @@ fix = {
 
 /*
  *  Fix CTRL macros
+ *
+ * Basically, what is supposed to be happening is that every
+ * _invocation_ of the "_CTRL()" or "CTRL()" macros is supposed to have
+ * its argument inserted into single quotes.  We _must_ do this because
+ * ANSI macro substitution rules prohibit looking inside quoted strings
+ * for the substitution names.  A side effect is that the quotes are
+ * inserted in the definitions of those macros as well.  So, the last
+ * three sed expressions are supposed to clean up the definitions, as
+ * long as those definitions are using "c", "g" or "x" as the macro
+ * argument :).  Yuck.
  */
 fix = {
     hackname = ioctl_fix_ctrl;