tcsh: import an Arch patch (merging the two patches into a single one) for fixing gcc5 optimisation

pkgs/shells/tcsh/avoid-gcc5-wrong-optimisation.patch

···
+From: christos <christos>
+Date: Thu, 28 May 2015 11:47:03 +0000
+Subject: [PATCH] avoid gcc-5 optimization malloc + memset = calloc (Fridolin
+Pokorny)
+
+---
+tc.alloc.c | 5 ++++-
+1 file changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/tc.alloc.c b/tc.alloc.c
+index b9aec63..c1cb330 100644
+--- a/tc.alloc.c
++++ b/tc.alloc.c
+@@ -348,10 +348,13 @@ calloc(size_t i, size_t j)
+ {
+ #ifndef lint
+     char *cp;
++    volatile size_t k;
+ 
+     i *= j;
+     cp = xmalloc(i);
+-    memset(cp, 0, i);
++    /* Stop gcc 5.x from optimizing malloc+memset = calloc */
++    k = i;
++    memset(cp, 0, k);
+ 
+     return ((memalign_t) cp);
+ #else

pkgs/shells/tcsh/default.nix

···
   version = "6.19.00";
   
   src = fetchurl {
-    urls = [ "ftp://ftp.funet.fi/pub/unix/shells/tcsh/${name}.tar.gz"
-             "http://ftp.funet.fi/pub/mirrors/ftp.astron.com/pub/tcsh/${name}.tar.gz" ];
+    urls = [ 
+             "http://ftp.funet.fi/pub/mirrors/ftp.astron.com/pub/tcsh/${name}.tar.gz" 
+             "ftp://ftp.astron.com/pub/tcsh/${name}.tar.gz" 
+             "ftp://ftp.funet.fi/pub/unix/shells/tcsh/${name}.tar.gz"
+             ];
     sha256 = "0jaw51382pqyb6d1kgfg8ir0wd3p5qr2bmg8svcmjhlyp3h73qhj";
   };
+
+  patches = [ ./avoid-gcc5-wrong-optimisation.patch ];
   
   buildInputs = [ ncurses ];