Add explanatory comments for iquote.patch as was done on f20

- The reason for this running patch is far from obvious.
- Helps code reviwers as the patch sometimes needs updating
- when doing rebases to nss that introduce new functions.

nss.spec

@@ -19,7 +19,7 @@
 Summary:          Network Security Services
 Name:             nss
 Version:          3.15.4
-Release:          3%{?dist}
+Release:          4%{?dist}
 License:          MPLv2.0
 URL:              http://www.mozilla.org/projects/security/pki/nss/
 Group:            System Environment/Libraries
@@ -86,6 +86,12 @@ Patch47:          utilwrap-include-templates.patch
 Patch48:          nss-versus-softoken-tests.patch
 # TODO remove when we switch to building nss without softoken
 Patch49:          nss-skip-bltest-and-fipstest.patch
+# This patch uses the gcc-iquote dir option documented at
+# http://gcc.gnu.org/onlinedocs/gcc/Directory-Options.html#Directory-Options
+# to place the in-tree directories at the head of the list of list of directories
+# to be searched for for header files. This ensures a build even when system 
+# headers are older. Such is the case when starting an update with API changes or even private export changes.
+# Once the buildroot aha been bootstrapped the patch may be removed but it doesn't hurt to keep it.
 Patch50:          iquote.patch
 
 %description
@@ -728,6 +734,9 @@ fi
 
 
 %changelog
+* Mon Jan 27 2014 Elio Maldonado <emaldona@redhat.com> - 3.15.4-4
+- Add explanatory comments for iquote.patch as was done on f20
+
 * Sat Jan 25 2014 Elio Maldonado <emaldona@redhat.com> - 3.15.4-3
 - Update pem sources to latest from nss-pem upstream
 - Pick up pem fixes verified on RHEL and applied upstream