Include wincrypt.h when compiling with OpenSSL on Windows

Include wincrypt.h when compiling with OpenSSL on Windows

... but undefine X509_NAME and X509_EXTENSIONS.

Fixes:

    x86_64-w64-mingw32-gcc -c -pipe -O2 -Wshadow -DWINVER=0x501   -mwindows
    -Wall -Ipcre  openssl.c -o openssl.o
    In file included from
    P:/msys64/mingw64/x86_64-w64-mingw32/include/windows.h:95,
                     from project.h:62,
                     from openssl.c:42:
    P:/msys64/mingw64/include/openssl/ssl.h:1611:5: error: expected
    specifier-qualifier-list before '(' token
     1611 |     X509_EXTENSIONS *tlsext_ocsp_exts;
          |     ^~~~~~~~~~~~~~~

when using OpenSSL 1.0.2.

Reported and partially submitted by: Hớ Hờ Hợ