[eigen] Quaternion Map Traits

[Jean Sreng <jean.sreng@xxxxxx>]

Hello,

By upgrading our codebase to Eigen 3.1, we spotted a bug in the 
definitions of Quaternion Map Traits. The Flags and Options used in 
these traits are incorrectly referring to the Flags/Options of 
Quaternion Coefficients instead of Map<Quaternion> Coefficients. This 
triggered an incorrect alignment flag on functions such as multiply.

The patch is available here (branch 3.1) but should transparently apply 
on 3.0 and default:

https://bitbucket.org/jsreng/eigen/commits/8b4bbc5304acf0505b297c485474b859

I can issue a pull request if it fits your workflow better.

Cheers,

--
Jean Sreng