Fine: "struct hello *world"

Not fine: "struct hello* world" (and variations)

Closes #5386

.. because checksrc's copyright year check stopped working.

Ref: https://github.com/curl/curl/pull/4547

Closes https://github.com/curl/curl/pull/4549

Classic MinGW still has _beginthreadex's return type as unsigned long
instead of uintptr_t [0]. uintptr_t is not even defined because of [1].

[0] https://sourceforge.net/p/mingw/mingw-org-wsl/ci/wsl-5.1-release/tree/mingwrt/include/process.h#l167
[1] https://sourceforge.net/p/mingw/mingw-org-wsl/ci/wsl-5.1-release/tree/mingwrt/include/process.h#l90

Bug: https://github.com/curl/curl/issues/2924#issuecomment-424334807
Closes https://github.com/curl/curl/pull/3051

As uintptr_t and HANDLE are always the same size, this warning is
harmless. Just silence it using an intermediate uintptr_t variable.

Closes https://github.com/curl/curl/pull/2908

Use LongToHandle to convert from long to HANDLE in the Win32
implementation.
This should fix the following warning when compiling with
MSVC 11 (2012) in 64-bit mode:
lib\curl_threads.c(113): warning C4306:
'type cast' : conversion from 'long' to 'HANDLE' of greater size

Closes https://github.com/curl/curl/pull/1717

Prior to this change (SET_)ERRNO mapped to GetLastError/SetLastError
for Win32 and regular errno otherwise.

I reviewed the code and found no justifiable reason for conflating errno
on WIN32 with GetLastError/SetLastError. All Win32 CRTs support errno,
and any Win32 multithreaded CRT supports thread-local errno.

Fixes https://github.com/curl/curl/issues/895
Closes https://github.com/curl/curl/pull/1589

In order to make the code style more uniform everywhere

Follow up to commit 7db9782dd6.