add initial CMake and Visual Studio build support

This moves the compatibility include files from include to
include/compat so we can use the awful MS C compiler
<../include/> trick to emulate the GNU #include_next extension.

This also removes a few old compat files we do not need anymore.

patches/ossl_typ.h.patch

@@ -1,15 +1,17 @@
 --- include/openssl/ossl_typ.h.orig	2015-07-06 13:21:18.788571423 -0700
 +++ include/openssl/ossl_typ.h	2015-07-06 13:24:14.906468003 -0700
-@@ -100,6 +100,20 @@
+@@ -100,6 +100,22 @@
  typedef struct ASN1_ITEM_st ASN1_ITEM;
  typedef struct asn1_pctx_st ASN1_PCTX;
 
 +#if defined(_WIN32) && defined(__WINCRYPT_H__)
++#ifndef LIBRESSL_INTERNAL
 +#ifdef _MSC_VER
 +#pragma message("Warning, overriding WinCrypt defines")
 +#else
 +#warning overriding WinCrypt defines
 +#endif
++#endif
 +#undef X509_NAME
 +#undef X509_CERT_PAIR
 +#undef X509_EXTENSIONS