This download contains all the XML and SDK files needed to create a new promotion called: Extra Strength. It provides Archery and Melee units with +1 strength, which is not a percentage increase. It is an integer increase and adds a new tag in the CIV4PromotionInfos.XML file:
I have made all the SDK changes very easy to find. Just look for "Additional Strength Mod".Code:<iExtraStrength>1</iExtraStrength>
Note: The mod has been fixed as of 08/31/2014.
Additional Strength Source Files 2016-10-05
Additional Strength Source Files