schur and rel unit tests
schur with 3 outputs and unit tests for all schur calls
correcting calls in routines using schur
remove pessimization in scalar pow
rework pow; pow_absi has been removed and integrated into pow_abs, and pow is now defined in terms of pow_abs even for integer cases. More tests, correct behaviour and more efficient implementations for integers, also support pow(int, int). fix #794
fix dispatch of pow_abs complex
Merge pull request #809 from jtlap/linalg_6b_schur

Linalg 6b schur
incorrect documentation of pow_abs