Fixes #110 Discount Coupon exception to exclude specials and sales

<a href='#crh-start'></a><a href='#crh-data-%7B%22processed%22%3A%20%5B%22https%3A//github.com/zencart/zc-v1-series/pull/111%23issuecomment-50283049%22%2C%20%22https%3A//github.com/zencart/zc-v1-series/pull/111%23issuecomment-50283166%22%2C%20%22https%3A//github.com/zencart/zc-v1-series/pull/111%23issuecomment-50283579%22%2C%20%22https%3A//github.com/zencart/zc-v1-series/pull/111%23issuecomment-50283616%22%2C%20%22https%3A//github.com/zencart/zc-v1-series/pull/111%23discussion_r15145815%22%5D%2C%20%22comments%22%3A%20%7B%22General%20Comment%22%3A%20%7B%22html_url%22%3A%20%22https%3A//github.com/zencart/zc-v1-series/pull/111%23issuecomment-50283049%22%2C%20%22comments%22%3A%20%5B%7B%22body%22%3A%20%22Fail%20to%20see%20how%20that%20is%20relevant.%20The%20code%20in%20question%20is%20procedural%2C%20and%20re-writing%20as%20a%20series%20of%20if%20clauses%20seems%20mindless.%22%2C%20%22created_at%22%3A%20%222014-07-27T19%3A28%3A40Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/227354%3F%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/zcwilt%22%7D%7D%2C%20%7B%22body%22%3A%20%22%3A%2B1%3A%20%22%2C%20%22created_at%22%3A%20%222014-07-27T19%3A33%3A00Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/227354%3F%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/zcwilt%22%7D%7D%2C%20%7B%22body%22%3A%20%22Agreed.%20This%20is%20procedural%20code.%20While%20a%20broader%20task%20of%20rewriting%20the%20entire%20admin%20is%20needed%20and%20scheduled%2C%20this%20PR%20is%20not%20that.%22%2C%20%22created_at%22%3A%20%222014-07-27T19%3A46%3A13Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/404472%3F%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/drbyte%22%7D%7D%2C%20%7B%22body%22%3A%20%22%3A%2B1%3A%20%3Ashipit%3A%20%22%2C%20%22created_at%22%3A%20%222014-07-27T19%3A48%3A09Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/404472%3F%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/drbyte%22%7D%7D%5D%2C%20%22title%22%3A%20%22General%20Comment%22%7D%2C%20%22Pull%2098ddede222848ccaf32e7b4f2a5363faddb21cee%20includes/modules/pages/discount_coupon/header_php.php%2021%22%3A%20%7B%22html_url%22%3A%20%22https%3A//github.com/zencart/zc-v1-series/pull/111%23discussion_r15145815%22%2C%20%22comments%22%3A%20%5B%7B%22body%22%3A%20%22It%27s%20a%20best%20practice%20to%20%5Bavoid%5D%28http%3A//c2.com/cgi/wiki%3FSwitchStatementsSmell%29%20%60switch%60%20blocks%20unless%20the%20fall-through%20functionality%20is%20needed.%22%2C%20%22created_at%22%3A%20%222014-07-19T20%3A48%3A10Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/1590605%3F%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/texdc%22%7D%7D%5D%2C%20%22title%22%3A%20%22File%3A%20includes/modules/pages/discount_coupon/header_php.php%3AL33-57%22%7D%7D%2C%20%22approved%22%3A%20%7B%22https%3A//github.com/drbyte%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/404472%3F%22%7D%7D%7D'></a>
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- [ ] <a href='#crh-comment-Pull 98ddede222848ccaf32e7b4f2a5363faddb21cee includes/modules/pages/discount_coupon/header_php.php 21'></a> <img src='http://www.codereviewhub.com/site/github-remaining.png' height=16 width=60>&nbsp;<b><a href='https://github.com/zencart/zc-v1-series/pull/111#discussion_r15145815'>File: includes/modules/pages/discount_coupon/header_php.php:L33-57</a></b>
- <a href='https://github.com/texdc'><img border=0 src='https://avatars.githubusercontent.com/u/1590605?size=16' height=16 width=16'></a> It's a best practice to [avoid](http://c2.com/cgi/wiki?SwitchStatementsSmell) `switch` blocks unless the fall-through functionality is needed.
- [x] <a href='#crh-comment-General Comment'></a> <img src='http://www.codereviewhub.com/site/github-completed.png' height=16 width=60>&nbsp;<b><a href='https://github.com/zencart/zc-v1-series/pull/111#issuecomment-50283049'>General Comment</a></b>
- <a href='https://github.com/zcwilt'><img border=0 src='https://avatars.githubusercontent.com/u/227354?size=16' height=16 width=16'></a> Fail to see how that is relevant. The code in question is procedural, and re-writing as a series of if clauses seems mindless.
- <a href='https://github.com/zcwilt'><img border=0 src='https://avatars.githubusercontent.com/u/227354?size=16' height=16 width=16'></a> :+1:
- <a href='https://github.com/drbyte'><img border=0 src='https://avatars.githubusercontent.com/u/404472?size=16' height=16 width=16'></a> Agreed. This is procedural code. While a broader task of rewriting the entire admin is needed and scheduled, this PR is not that.
- <a href='https://github.com/drbyte'><img border=0 src='https://avatars.githubusercontent.com/u/404472?size=16' height=16 width=16'></a> :+1: :shipit:


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