[Ada] Remove dependency on Win32 GDI (Graphical Interface)

[Ada] Remove dependency on Win32 GDI (Graphical Interface)

CommandLineToArgvW drags a dependency on SHELL32.DLL and thus GDI32.DLL.
By loading GDI32.DLL some default GDI objects are allocated. On some
Windows versions this cause the use of a lock on the graphical interface
during process termination. This can impact parallelism significantly as
termination of processes is serialized.

2019-07-08  Nicolas Roche  <roche@adacore.com>

gcc/ada/

	* rtinit.c (__gnat_runtime_initialize): Remove dependency on
	CommandLineToArgvW.

From-SVN: r273214