libgolang: Provide select(vector<_selcase>)

We already provide select for array and std::initializer_list. However
when cases are constructed at runtime dynamically both array and
initializer_list are not convenient to use.

-> Provide select() overload that accepts vector<_selcase>.

This functionality will soon be used in C version of context package.

golang/libgolang.h

@@ -295,6 +295,7 @@ LIBGOLANG_API extern void (*_tblockforever)(void);
 #include <memory>
 #include <type_traits>
 #include <utility>
+#include <vector>
 
 namespace golang {
 
@@ -442,6 +443,11 @@ int select(const _selcase (&casev)[N]) {
     return _chanselect(&casev[0], N);
 }
 
+static inline                       // select(vector<casev>)
+int select(const std::vector<_selcase> &casev) {
+    return _chanselect(&casev[0], casev.size());
+}
+
 // defer(f) mimics `defer f()` from golang.
 // NOTE contrary to Go f is called at end of current scope, not function.
 #define defer(f) golang::_deferred _defer_ ## __COUNTER__ (f)