Cleaned knc-i1x16.h

* Complete int32, float & doublei
* int64 is partially complete 
* Few fails in __load<64> & int64 ops (`grep -Hn 'knc::fails'  knc-i1x16.h`)
* Removed unused macros

Here is run_test output:

    ./run_tests.py -j 10 --target=generic-16 --generics-include=./examples/intrinsics/knc-i1x16.h --compiler=icpc
    ispc compiler: ./ispc 
    
    Using test compiler: Intel(r) SPMD Program Compiler (ispc), 1.5.1dev (build commit 2741e3c1d09591bc @ 20131003, LLVM 3.3)
    Using C/C++ compiler: icpc (ICC) 14.0.0 20130728
    
    Running 10 jobs in parallel. Running 1206 tests.
    Compilation of test ./tests/ptr-assign-lhs-math-1.ispc failed            
      %ins46 = and i512 %0, -18446744069414584321
    ispc: cbackend.cpp:4625: virtual bool BitcastCleanupPass::runOnBasicBlock(llvm::BasicBlock&): Assertion `opBc != __null' failed.
    main.cpp(223): FATAL ERROR: Unhandled signal sent to process; terminating.
    ***
    *** Please file a bug report at https://github.com/ispc/ispc/issues
    *** (Including as much information as you can about how to reproduce this error).
    *** You have apparently encountered a bug in the compiler that we'd like to fix!
    ***
    Test ./tests/test-141.ispc failed (return code 1)                        
    ./tests/test-141.ispc.run: value 8 disagrees: returned 0.000000 [0x0p+0], expected 1.000000 [0x1p+0]
    ./tests/test-141.ispc.run: value 10 disagrees: returned 0.000000 [0x0p+0], expected 1.000000 [0x1p+0]
    ./tests/test-141.ispc.run: value 13 disagrees: returned 0.000000 [0x0p+0], expected 1.000000 [0x1p+0]
    ./tests/test-141.ispc.run: value 14 disagrees: returned 0.000000 [0x0p+0], expected 1.000000 [0x1p+0]

     Done 1206 / 1206 [./tests/launch-2.ispc]                                
    1 / 1206 tests FAILED compilation:
            ./tests/ptr-assign-lhs-math-1.ispc
    1 / 1206 tests FAILED execution:
            ./tests/test-141.ispc
    NEW RUNFAILS:
            ./tests/test-141.ispc
    NEW COMPFAILS:
            ./tests/ptr-assign-lhs-math-1.ispc