[patch, fortran] fix for PR 60780, PR 40958

[Russell Whitesides]

Patch below prevents printing of duplicate statements in module files.
Without it module files grow exponentially in size with nested use of 
modules that contain equivalence statements.  Tested on x86-64-linux.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60780
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40958

2015-05-14

     PR fortran 60780
     * module.c (load_equiv) : add check for duplicate modules


Index: module.c
===================================================================
--- module.c	(revision 223202)
+++ module.c	(working copy)
@@ -4479,8 +4479,8 @@
  static void
  load_equiv (void)
  {
-  gfc_equiv *head, *tail, *end, *eq;
-  bool unused;
+  gfc_equiv *head, *tail, *end, *eq, *equiv;
+  bool unused, duplicate;

    mio_lparen ();
    in_load_equiv = true;
@@ -4523,8 +4523,20 @@
  	  }
        }

-    if (unused)
+    /* Check for duplicate equivalences being loaded from different 
modules */
+    duplicate = false;
+    for (equiv = gfc_current_ns->equiv; equiv; equiv = equiv->next)
        {
+        if (equiv->module && head->module
+              && strcmp (equiv->module, head->module) == 0)
+          {
+            duplicate = true;
+            break;
+          }
+      }
+
+    if (unused || duplicate)
+      {
  	for (eq = head; eq; eq = head)
  	  {
  	    head = eq->eq;