Follow-up to: 4027bd72d9

- When creating a directory hierarchy do not error when mkdir fails due
  to error EACCESS (13) "access denied".

Some file systems allow for directory traversal; in this case that it
should be possible to create child directories when permission to the
parent directory is restricted.

This is a regression caused by me in f16bed0 (precedes curl-7_61_1).
Basically I had assumed that if a directory already existed it would
fail only with error EEXIST, and not error EACCES. The latter may
happen if the directory exists but has certain restricted permissions.

Reported-by: mbeifuss@users.noreply.github.com

Fixes https://github.com/curl/curl/issues/4796
Closes https://github.com/curl/curl/pull/4797

The function does not return the same value as snprintf() normally does,
so readers may be mislead into thinking the code works differently than
it actually does. A different function name makes this easier to detect.

Reported-by: Tomas Hoger
Assisted-by: Daniel Gustafsson
Fixes #3296
Closes #3297

- replace tabs with spaces where possible
- remove line ending spaces
- remove double/triple newlines at EOF
- fix a non-UTF-8 character
- cleanup a few indentations/line continuations
  in manual examples

Closes https://github.com/curl/curl/pull/3037

Patch-by: Jay Satiro
Detected by Coverity
Fixes #2739
Closes #2912

djgpp do have 'mkdir(dir, mode)'. Other DOS-compilers does not 
But djgpp seems the only choice for MSDOS anyway.

PellesC do have a 'F_OK' defined in it's <unistd.h>.

Update year in Copyright.

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

Reported-by: Ryan Scott

Fixes #1007