* fix broken code link

resolves  #15344

* Update stitcher.markdown

* update 3.4 link

* jas_stream: Add definition for L_tmpnam if missing

uClibc-ng for some reason does not provide a definition when some
deprecated APIs are disabled. Value taken from the musl libc.

* 3rdparty: move uClibc-ng workaround into config file

Found using `codespell -q 3 -S ./3rdparty -L activ,amin,ang,atleast,childs,dof,endwhile,halfs,hist,iff,nd,od,uint`

backporting of commit: ec43292e

Found via `codespell -q 3 -S ./3rdparty,./modules -L amin,ang,atleast,dof,endwhile,hist,uint`

backporting of commit: 32aba5e6

* WINCE 8.0 requires ARMv7 Thumb2 and thus have NEON instructions

* Only add NEON if on _ARM_

Convert HOG from SSE SIMD to HAL - 35-45% faster on Power (VSX) (#15199)

* Convert SSE SIMD to HAL. 35-45% improvement for Power (VSX)

* Remove CV_NEON code. Use v_floor instead of 3 lines of code.

* Invert comparison logic to simplify code.

* Change initialization from v_load to constructor type.

* Remove unavoidable print of CV error

The return value covers whether the device exists.

This might be better hidden behind a debug flag, but I couldn't work out how to do that nicely.

* Use `CV_LOG_WARNING` macro to log rather than removing it entirely

  * add -Wno-psabi when using GCC 6
  * add -Wundef for CUDA 10
  * add -Wdeprecated-declarations when using GCC 7
  * add -Wstrict-aliasing and -Wtautological-compare for GCC 7
  * replace cudaThreadSynchronize with cudaDeviceSynchronize

Implement cvRound using inline asm. No compiler support
exists today to properly optimize this. This results in
about a 4x speedup over the default rounding. Likewise,
simplify the growing number of rounding function overloads.

For P9 enabled targets, utilize the classification
testing instruction to test for Inf/Nan values. Operation
speedup is about 1.2x for FP32, and 1.5x for FP64 operands.

For P8 targets, fallback to the GCC nan inline. It provides
a 1.1/1.4x improvement for FP32/FP64 arguments.

Add a new macro definition OPENCV_USE_FASTMATH_GCC_BUILTINS to enable
usage of GCC inline math functions, if available and requested by the
user.

Likewise, enable it for POWER. This is nearly always a substantial
improvement over using integer manipulation as most operations can
be done in several instructions with no branching. The result is a
1.5-1.8x speedup in the ceil/floor operations.

1. As tested with AT 12.0-1 (GCC 8.3.1) compiler on P9 LE.

Add a basic sanity test to verify the rounding functions
work as expected.

Likewise, extend the rounding performance test to cover the
additional float -> int fast math functions.