[GSoC 2019] Improve the performance of JavaScript version of OpenCV (OpenCV.js)

* [GSoC 2019]

Improve the performance of JavaScript version of OpenCV (OpenCV.js):
1. Create the base of OpenCV.js performance test:
     This perf test is based on benchmark.js(https://benchmarkjs.com). And first add `cvtColor`, `Resize`, `Threshold` into it.
2. Optimize the OpenCV.js performance by WASM threads:
     This optimization is based on Web Worker API and SharedArrayBuffer, so it can be only used in browser.
3. Optimize the OpenCV.js performance by WASM SIMD:
     Add WASM SIMD backend for OpenCV Universal Intrinsics. It's experimental as WASM SIMD is still in development.

* [GSoC2019] 

1. use short license header
2. fix documentation node issue
3. remove the unused `hasSIMD128()` api

* [GSoC2019]

1. fix emscripten define
2. use fallback function for f16

* [GSoC2019]

Fix rebase issue

* 3rdparty: libpng v1.6.37 MSA patch (pr15422)

original files: https://github.com/glennrp/libpng/tree/v1.6.37/mips

* 3rdparty: libwebp MSA asm patch (pr15422)

* Added MSA implementations for mips platforms. Intrinsics for MSA and build scripts for MIPS platforms are added.
Signed-off-by: Fei Wu <fwu@wavecomp.com>

* Removed some unused code in mips.toolchain.cmake.
Signed-off-by: Fei Wu <fwu@wavecomp.com>

* Added comments for mips toolchain configuration and disabled compiling warnings for libpng.
Signed-off-by: Fei Wu <fwu@wavecomp.com>

* Fixed the build error of unsupported opcode 'pause' when mips isa_rev is less than 2.
Signed-off-by: Fei Wu <fwu@wavecomp.com>

* 1. Removed FP16 related item in MSA option defines in OpenCVCompilerOptimizations.cmake.
2. Use CV_CPU_COMPILE_MSA instead of __mips_msa for MSA feature check in cv_cpu_dispatch.h.
3. Removed hasSIMD128() in intrin_msa.hpp.
4. Define CPU_MSA as 150.
Signed-off-by: Fei Wu <fwu@wavecomp.com>

* 1. Removed unnecessary CV_SIMD128_64F guarding in intrin_msa.hpp.
2. Removed unnecessary CV_MSA related code block in dotProd_8u().
Signed-off-by: Fei Wu <fwu@wavecomp.com>

* 1. Defined CPU_MSA_FLAGS_ON as "-mmsa".
2. Removed CV_SIMD128_64F guardings in intrin_msa.hpp.
Signed-off-by: Fei Wu <fwu@wavecomp.com>

* Removed unused msa_mlal_u16() and msa_mlal_s16 from msa_macros.h.
Signed-off-by: Fei Wu <fwu@wavecomp.com>

* remove old BUILD_opencv_java option

* replace old build_java option with new BUILD_JAVA option

* issue 5769 fixed: cv::stereoRectify fails if given inliers mask of type vector<uchar>

* issue5769 fix using reshape and add regression test

* regression test with outlier detection, testing vector and mat data

* Size comparision of wrong vector within CV_Assert in regression test corrected

* cleanup test code

ISA 2.07 (aka POWER8) effectively extended the expanding multiply
operation to word types. The altivec intrinsics prior to gcc 8 did
not get the update.

Workaround this deficiency similar to other fixes.

This was exposed by commit 33fb253a
which leverages the int -> dword expanding multiply.

This fixes Issue #15506