Determine version of Metis library. Apparently, at least version 5.x is needed for Eigen/MetisSupport.
Marked some internal variables as advanced

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)

(grafted from 501e6f168055a3d7782730c1ade00b8f853a1a0d)

UmfPack support: fix redundant evaluation/copies when calling compute() and support generic expressions as input

(grafted from 9d33229cfb960f4272de8dad046f75873723751e)

(grafted from 8ba3b2cf2df84e9e69bc0b7ee3172ed4833cdb47)

(grafted from c303363d178956db60ea7a21c88b36b20f5d6560)

Fix Hyperplane::Through(a,b,c) when points are aligned or identical. We use the stratgey as in Quaternion::setFromTwoVectors.
(grafted from d9af749994e161380b1bc281dccc0be93fe3f082)

(grafted from 1d72cb9b08c13d0c344fdad2a43a91aaf89fa7c5)

re-enable usage of ProductBase::m_result and workaround a compilation failure when m_result is too large but unused

psqrt(NaN) and psqrt(-1) shall return NaN if EIGEN_FAST_MATH==0

(grafted from 3e1f580fdb6c5bf43ad9804f1469ac1e4bb313d6)

(grafted from 1b9354d4370951e8cd66eac5df3eba34d05e44d6)

(grafted from 0e64f7b3e7d70115247257d1d123a29491483df7)

(grafted from d6bf18e70f68e738554cbf61576da70e2d99bea4)

(transplanted from 9e52b49b3a5801ce508121dc799edfb2cdeea468)

manually ported from cbe72de483f9

Bug 879: tri1 = mat * tri2 was compiling and running incorrectly if tri2 was not numerically triangular. Workaround the issue by evaluating mat*tri2 into a temporary.

(grafted from f12914580cba7071edaabefe702d7838f8b021f4)

(grafted from 4a218338fff36634b9073ee60ca99f4dae704f31)