comctl32.def: Add `LoadIconMetric`

According to [MSDN] [1] 'comctl32.dll' exports function
`LoadIconMetric`, which is currently declared in mingw-w64's
'commctrl.h', but is missed in exporting declarations. This patch fixes
that.

[1]:
https://msdn.microsoft.com/en-us/library/windows/desktop/bb775701(v=vs.85).aspx
"LoadIconMetric function"

Signed-off-by: Ruslan Garipov <ruslanngaripov@gmail.com>
(cherry picked from commit 723bef4de85bc777a9391ce9acc42ebb25d5fc62)
Signed-off-by: Jonathan Yong <10walls@gmail.com>
2 files changed