ImVector: Added ImVector::push_front helper.

imgui.h

@@ -983,6 +983,7 @@ public:
 
     inline void                 push_back(const value_type& v)  { if (Size == Capacity) reserve(_grow_capacity(Size+1)); Data[Size++] = v; }
     inline void                 pop_back()                      { IM_ASSERT(Size > 0); Size--; }
+    inline void                 push_front(const value_type& v) { if (Size == 0) push_back(v); else insert(Data, v); }
 
     inline iterator             erase(const_iterator it)        { IM_ASSERT(it >= Data && it < Data+Size); const ptrdiff_t off = it - Data; memmove(Data + off, Data + off + 1, ((size_t)Size - (size_t)off - 1) * sizeof(value_type)); Size--; return Data + off; }
     inline iterator             insert(const_iterator it, const value_type& v)  { IM_ASSERT(it >= Data && it <= Data+Size); const ptrdiff_t off = it - Data; if (Size == Capacity) reserve(Capacity ? Capacity * 2 : 4); if (off < (int)Size) memmove(Data + off + 1, Data + off, ((size_t)Size - (size_t)off) * sizeof(value_type)); Data[off] = v; Size++; return Data + off; }