address win32 build issues

- Replace external -DOPENSSL/-DPKCS11CRYPTO with properly AC_DEFINEd
  HAVE_OPENSSL/HAVE_PKCS11
- Don't enforce the crypto provider from platform.h, just from dst_api.c
  and configure scripts

util/mksymtbl.pl

@@ -103,6 +103,7 @@ sub lhex {
 }
 
 print TBLFILE "/*\n * Generated by $rev \n */\n";
+print TBLFILE "#include <config.h>\n";
 print TBLFILE "#include <isc/backtrace.h>\n";
 print TBLFILE "const int isc__backtrace_nsymbols = $nsyms;\n";
 print TBLFILE "const isc_backtrace_symmap_t isc__backtrace_symtable[] = {\n";