Fix minor compatibility corner cases with the posix counterpart.

In D12041#229807, @bu5hm4n wrote:

Patch does not apply ...

Fix patch to apply to HEAD

Add tests and fix bugs

Address raster's review comments

Fix undefined behavior in eina_thread_self

Use native windows threads in mingw

Address review comments

Fix struct layout compatibility

In D12022#229393, @vtorri wrote:

i've looked at https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file#fully-qualified-vs-relative-paths and i indeed see it can begin with \ (but not /) :

"A file name is relative to the current directory if it does not begin with one of the following etc... "
"A single backslash, for example, "\directory" or "\file.txt". This is also referred to as an absolute path."

i don't know if you should also consider /

Update the patch based on reviewer feedback

Fix typo

Fix patch update

Fix negative path length calculation

In D11993#228976, @vtorri wrote:

@walac your prefer this patch which modifies 143 files, ONLY for eina, to my patch, which modifies 5 files for 4 libraries, with the same result ?? that's crazy

In D11993#228977, @vtorri wrote:

do you realize that, with this kind of changes, you are going to change almost all the files of the EFL ?

That patch seems a step towards in the right direction IMHO. Things get tricky when EFL try to use each other since, in some places, EAPI must be __declspec(dllimport) and in others __declspec(dllexport), which leads walking on thin ice by playing around with the preprocessor. I understand that each library should define its XXX_API macro. The static library support is a win, but not the main point of the patch.

In D11970#228390, @stefan_schmidt wrote:

Gettign of a tons of errors with this patch and cxx bindings enabled. One example (there are more):

[219/398] Compiling C++ object 'src/tests/eina_cxx/6b3491e@@eina_cxx_suite@exe/eina_cxx_suite.cc.o'
In file included from ../src/tests/eina_cxx/eina_cxx_suite.h:8,
                 from ../src/tests/eina_cxx/eina_cxx_suite.cc:20:
../src/tests/eina_cxx/../efl_check.h: In function ‘int _efl_test_option_disp(int, char**, const Efl_Test_Case*)’:
../src/tests/eina_cxx/../efl_check.h:137:23: warning: ISO C++ forbids converting a string constant to ‘char*’ [-Wwrite-strings]
  137 |              nav[0] = "valgrind";
      |                       ^~~~~~~~~~
../src/tests/eina_cxx/../efl_check.h:138:23: warning: ISO C++ forbids converting a string constant to ‘char*’ [-Wwrite-strings]
  138 |              nav[1] = "--trace-children=yes";

Make C++ compiler happy

@vtorri done

Replace malloc by alloca

Remove all references to errno in eina_test_file.c