Generate tables from df_dm

[rountree]

The manual approach to generating cross-references survives in util/mapping.h.

std::vector<std::string> df_dm is a list of df_dms with their associated tables.

std::vector<std::string> tables is a list of tables with their associated df_dms.

Trying to update both when a new version of the Intel manual drops is proving to be excessively error-prone. Use one to generate the other. (The former is easier to read on the screen, the latter might be easier to update as new architectures are added.)