Simplify libcurl initialization by using CURL_GLOBAL_ALL

Using anything else is not recommended by libcurl documentation and it's
not clear why would we need it, so just follow the official advice and
pass CURL_GLOBAL_ALL.

src/common/webrequest_curl.cpp

@@ -537,11 +537,7 @@ wxVersionInfo  wxWebSessionCURL::GetLibraryVersionInfo()
 // static
 void wxWebSessionCURL::InitializeCURL()
 {
-    long initFlags = CURL_GLOBAL_SSL;
-#ifdef WIN32
-    initFlags |= CURL_GLOBAL_WIN32;
-#endif // WIN32
-    if ( curl_global_init(initFlags) )
+    if ( curl_global_init(CURL_GLOBAL_ALL) )
         wxLogError("libcurl could not be initialized");
 }