curl_setup_once: Remove ERRNO/SET_ERRNO macros

[jay]

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 #895

[mention-bot]

@jay, thanks for your PR! By analyzing the history of the files in this pull request, we identified @aYasuharuYamada, @bagder and @yangtse to be potential reviewers.

[coveralls]

Coverage decreased (-73.4%) to 0.0% when pulling 7be1ff7fa16a4a3a06b2e046a216192e318f37aa on jay:remove_ERRNO_macro into 65ca030 on curl:master.

[bagder]

Seems you forgot something in lib/memdebug.c causing build errors.

[jay]

Seems you forgot something in lib/memdebug.c causing build errors.

fixed, thanks. tested with CPPFLAGS=-DMEMDEBUG_LOG_SYNC and --enable-debug

[coveralls]

Coverage decreased (-73.8%) to 0.0% when pulling 1b0e2564bf770f38d83ed36e112650f4e13b3d8c on jay:remove_ERRNO_macro into b778ae4 on curl:master.

[bagder]

strerror.c: In function 'Curl_strerror':
strerror.c:634:3: error: unknown type name 'DWORD'
strerror.c:640:3: error: implicit declaration of function 'GetLastError' [-Werror=implicit-function-declaration]
strerror.c:640:3: warning: nested extern declaration of 'GetLastError' [-Wnested-externs]
strerror.c:730:5: error: implicit declaration of function 'SetLastError' [-Werror=implicit-function-declaration]
strerror.c:730:5: warning: nested extern declaration of 'SetLastError' [-Wnested-externs]

[jay]

Ok I think I got them all. The functions in strerror.c can modify errno so it's saved beforehand, and now that the Windows API error code is separate from errno it should be preserved as well. I had changed the code to do that but did not guard one of the sections as Windows, oops. I've since made some more robust changes to correct it, we'll see what the CI says..

[coveralls]

Coverage decreased (-0.01%) to 73.8% when pulling e8ced6c on jay:remove_ERRNO_macro into 922f800 on curl:master.

[MarcelRaad]

@jay Seems like you pushed an older version of this - the changes to memdebug.c and strerror.c are missing in af02162.

[gvanem]

@MarcelRaad Confirmed. Patch:

--- a/memdebug.c 2017-07-10 11:00:17
+++ b/memdebug.c 2017-07-10 10:27:25
@@ -147,7 +147,7 @@
                 source, line, func);
         fflush(logfile); /* because it might crash now */
       }
-      errno = ENOMEM;
+      SET_ERRNO(ENOMEM);
       return TRUE; /* RETURN ERROR! */
     }
     else

[jay]

Thanks guys, I had mistakenly committed an older draft because my repos were out of sync. I just committed the rest in c5e87fd, so there is now no difference between the current code and the changes that were approved in the final draft.