COMP: Increase template depth for gcc.

Some gcc compilers have a limit template depth of 50, and UKF
uses Eigen that requires deeper template depths.  This version
checks to verify that the flag is valid, and then uses
a template depth of 127.
Merge pull request #18 from BRAINSia/IncreaseTemplateDepth

COMP: Increase template depth for gcc.
COMP: REVERT Increase template depth for gcc.

This reverts commit e8ac38e971e4e6806204db10dd2a2720f79241b5.

The problem was that Slicer was explicitly restricting the template
depth to -ftemplate-depth-50 as was needed for the gcc3 compilers.

This was code copied from ITKv3 many years ago.
Merge pull request #19 from BRAINSia/RevertCommit

COMP: REVERT Increase template depth for gcc.