Port to ppc64le architecture

[vt-alt]

Tested on actual hardware — on gcc135 GCC Compile Farm's box, also tested as part of downstream liboqs project on ALT Linux ppc64le hardware.

[gcc135 PQCrypto-SIDH]$ arch
ppc64le

[gcc135 PQCrypto-SIDH]$ make ARCH=PPC64LE CC=gcc test434 test503 test610 test751
sike434/test_SIKE


TESTING ISOGENY-BASED KEY ENCAPSULATION MECHANISM SIKEp434
--------------------------------------------------------------------------------------------------------

  KEM tests .................................................... PASSED


BENCHMARKING ISOGENY-BASED KEY ENCAPSULATION MECHANISM SIKEp434
--------------------------------------------------------------------------------------------------------

  Key generation runs in .......................................   24951193 nsec
  Encapsulation runs in ........................................   40648243 nsec
  Decapsulation runs in ........................................   43434086 nsec
sike503/test_SIKE


TESTING ISOGENY-BASED KEY ENCAPSULATION MECHANISM SIKEp503
--------------------------------------------------------------------------------------------------------

  KEM tests .................................................... PASSED


BENCHMARKING ISOGENY-BASED KEY ENCAPSULATION MECHANISM SIKEp503
--------------------------------------------------------------------------------------------------------

  Key generation runs in .......................................   36288768 nsec
  Encapsulation runs in ........................................   59632179 nsec
  Decapsulation runs in ........................................   63485491 nsec
sike610/test_SIKE


TESTING ISOGENY-BASED KEY ENCAPSULATION MECHANISM SIKEp610
--------------------------------------------------------------------------------------------------------

  KEM tests .................................................... PASSED


BENCHMARKING ISOGENY-BASED KEY ENCAPSULATION MECHANISM SIKEp610
--------------------------------------------------------------------------------------------------------

  Key generation runs in .......................................   71338956 nsec
  Encapsulation runs in ........................................  131142502 nsec
  Decapsulation runs in ........................................  131886899 nsec
sike751/test_SIKE


TESTING ISOGENY-BASED KEY ENCAPSULATION MECHANISM SIKEp751
--------------------------------------------------------------------------------------------------------

  KEM tests .................................................... PASSED


BENCHMARKING ISOGENY-BASED KEY ENCAPSULATION MECHANISM SIKEp751
--------------------------------------------------------------------------------------------------------

  Key generation runs in .......................................  131369779 nsec
  Encapsulation runs in ........................................  212954982 nsec
  Decapsulation runs in ........................................  228760678 nsec

[ghost]

All CLA requirements met.