_WINDLL being defined doesn't mean libssh2 was built as a DLL (libssh2#1578) (libssh2#1793)

libssh2#1578
WINDLL means that the current project using this library is a DLL; not
that this library was built as a DLL. This check for _WINDLL is
incorrect, and the LIBSSH2_EXPORTS flag should be used instead.

Description of problem - build libssh2 as a static library to be
included in a dynamic library; if libssh2 uses _WINDLL then the names
generated are `__imp_*` which do not exist in the static build of the
library.

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Co-authored-by: d3x0r <d3x0r@no-reply.github.com>

Author: 2 people

include/libssh2.h

@@ -105,7 +105,7 @@ extern "C" {
 /* Allow alternate API prefix from CFLAGS or calling app */
 #ifndef LIBSSH2_API
 # ifdef _WIN32
-#  if defined(LIBSSH2_EXPORTS) || defined(_WINDLL)
+#  ifdef LIBSSH2_EXPORTS
 #   ifdef LIBSSH2_LIBRARY
 #    define LIBSSH2_API __declspec(dllexport)
 #   else