- cleaner use of OpenMP (no code duplication anymore)

using a macro and _Pragma.
- use OpenMP also in cacheOptimalProduct and in the
  vectorized paths as well
- kill the vector assignment unroller. implement in
  operator= the logic for assigning a row-vector in
  a col-vector.
- CMakeLists support for building tests/examples
  with -fopenmp and/or -msse2
- updates in bench/, especially replace identity()
  by ones() which prevents underflows from perturbing
  bench results.

CMakeLists.txt

@@ -8,6 +8,14 @@ SET(CMAKE_INCLUDE_CURRENT_DIR ON)
 IF(CMAKE_COMPILER_IS_GNUCXX)
   IF(CMAKE_SYSTEM_NAME MATCHES Linux)
     SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pedantic -Wnon-virtual-dtor -Wno-long-long -ansi -Wundef -Wcast-align -Wchar-subscripts -Wall -W -Wpointer-arith -Wwrite-strings -Wformat-security -fno-exceptions -fno-check-new -fno-common -fstrict-aliasing")
+    IF(TEST_OPENMP)
+      SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fopenmp")
+      MESSAGE("Enabling OpenMP in tests/examples")
+    ENDIF(TEST_OPENMP)
+    IF(TEST_SSE2)
+      SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse2")
+      MESSAGE("Enabling SSE2 in tests/examples")
+    ENDIF(TEST_SSE2)
   ENDIF(CMAKE_SYSTEM_NAME MATCHES Linux)
 ENDIF(CMAKE_COMPILER_IS_GNUCXX)