mscoree: Invoke installed win32 mono runtime or exec mono native for .NET executables (try 3)

[Paul Chitescu]

Changelog: mscoree: Invoke installed win32 mono runtime or exec mono native 
for .NET executables.

The code is inspired by the one in winebrowser.

Several alternatives can be provided in Registry, separated by commas. For 
each an attempt to execute it (spawnvp with OVERLAY flag set). The exception 
is the keyword MONOEMBED that will try to locate and dynamically load an 
installed Win32 mono.

The Registry key used is:

[HKCU\Software\Wine\mscoree]
"Runtimes"="MONOEMBED,/usr/bin/mono,mono"

By default MONOEMBED is preferred as it seems to provide best compatibility.

Setting the "Runtimes" value to an empty string will disable this feature and 
render .NET executables unrunable.

This is the 3rd version of the patch which tries to load mono more robustly 
and also dropped the WIN32_LEAN_AND_MEAN.

Paul