Add a new section on maintainability

06-Considering_Portability.md

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+# Considering Portability
+
+## Know Your Types
+
+Most portability issues that generate warnings are because we are not careful about our types. Standard library and arrays are indexed with `size_t`. Standard container sizes are reported in `size_t`. If you get the handling of `size_t` wrong, you can create subtle lurking 64-bit issues that arise only after you start to overflow the indexing of 32-bit integers. char vs unsigned char.
+
+http://www.viva64.com/en/a/0010/