Modified check for Windows (and poll.h)

Newest versions of libmysqlclient and the MariaDB C connector no longer
export the __WIN__ macro. If this macro is not present we would not
compile in the poll.h-based async-support. Changed to use the _WIN32
macro instead. Thanks to Sergei Golubchik for suggesting the fix.

Changes

@@ -1,3 +1,9 @@
+2016-??-?? Patrick Galbraith, Michiel Beijen, DBI/DBD community (4.037_01)
+* Newest versions of libmysqlclient and the MariaDB C connector no longer
+  export the __WIN__ macro. If this macro is not present we would not
+  compile in the poll.h-based async-support. Changed to use the _WIN32
+  macro instead. Thanks to Sergei Golubchik for suggesting the fix.
+
 2016-10-03 Patrick Galbraith, Michiel Beijen, DBI/DBD community (4.037)
 * Security release to patch possible buffer overflow in prepared
   statements. Reported and fixed by Pali Rohár. This vulnerability

dbdimp.h

@@ -27,7 +27,7 @@
 /* For now, we hardcode this, but in the future,
  * we can detect capabilities of the MySQL libraries
  * we're talking to */
-#if defined(__WIN__)
+#if defined(_WIN32)
 #define MYSQL_ASYNC 0
 #else
 #define MYSQL_ASYNC 1
@@ -235,7 +235,7 @@ typedef struct imp_sth_fbh_st {
     int            charsetnr;
     double         ddata;
     int32_t        ldata;
-#if MYSQL_VERSION_ID < FIELD_CHARSETNR_VERSION 
+#if MYSQL_VERSION_ID < FIELD_CHARSETNR_VERSION
     unsigned int   flags;
 #endif
 } imp_sth_fbh_t;