Change the default base address for x86_64

This might break things, but it turns out several Windows libraries like
to be loaded at 0x180000000.

This causes a problem, because `msys-2.0.dll` loads at `0x180040000` and
expects `0x180000000-0x180040000` to be available. A problem arises when
Antiviruses (or other DLL hooking mechanisms) load a DLL whose preferred
load address is `0x180000000` and fits in size before `0x180010000`:

1. `msys-2.0.dll` loads and fills `0x180010000-0x180040000` assuming no
   shared console structure is going to be needed.

2. Another DLL loads and fills `0x180000000-0x18000xxxx`

3. `msys-2.0.dll` tries to load `0x180000000-0x180010000` but it's not
   available. It falls back to another address, but down the line
   something else fails.

This bug triggers when using subshells (e.g.: `git clone --recursive`).

The MSYS2 runtime should be able to work around the address conflict,
but the code is failing in some way or other...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Mikael Larsson <95430516+chirpnot@users.noreply.github.com>

Author: chirpnot

winsup/cygwin/x86_64.din

@@ -1,4 +1,4 @@
-LIBRARY "msys-2.0.dll" BASE=0x180040000
+LIBRARY "msys-2.0.dll" BASE=0x210040000
 
 EXPORTS
 #Exported variables