A saving of "errno" became standard-compliant.

A variable was added for the issue "macro to save errno before write() while
using VERBOSE".
https://github.com/dermesser/libsocket/commit/b392310#L0L158

Unfortunately, a name was chosen which did not fit to the expected naming
convention of the C language standard. This detail was fixed by the deletion
of a leading double underscore.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Another preprocessor symbol became standard-compliant.

The preprocessor symbol "_MIXED" did not fit to the expected naming convention
of the C language standard. This detail was fixed by the deletion of
the leading underscore.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Merge pull request #14 from elfring/fix_reserved_identifier_violations

Fix reserved identifier violations