Update mpreal version.

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branch : 3.2
Adding missing OPENGL_LIBRARIES for openglsupport test. Also adding OpenGL include directories as a better pratice even though these are system include directories in most systems.
(grafted from 1a0b070721bc403eefb6a1cc28c78169e8518715)

--HG--
branch : 3.2
extra : source : 1a0b070721bc403eefb6a1cc28c78169e8518715
Determine version of Metis library. Apparently, at least version 5.x is needed for Eigen/MetisSupport.
Marked some internal variables as advanced

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branch : 3.2
extra : source : 86e4da678299b3ef36e024c5efe67480f775219c
Define EIGEN_NO_EIGEN2_DEPRECATED_WARNING in eigen2support unit tests

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branch : 3.2
Remove unused variables in eigen2support.

--HG--
branch : 3.2
Remove unused typedefs and variables

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branch : 3.2
Workaround warning when EIGEN_STACK_ALLOCATION_LIMIT==0

--HG--
branch : 3.2
Fix out-of-bounds write

--HG--
branch : 3.2
Disable another Eigen2 deprecated warning

--HG--
branch : 3.2
Disable yet another Eigen2 deprecated warning

--HG--
branch : 3.2
Big 853: replace enable_if in Ref<> ctor by static assertions and add failtests for Ref<>

--HG--
branch : 3.2
extra : source : 06d4fff20a9371aa2866f9aa959047dd3c5b740d