Runtime test to reproduce threadpool+ProcessExit issue

Do make test-process-exit to run
Fixes threadpool+ProcessExit problem

The threadpool was being shutdown too early, before the ProcessExit event was fired.
This led to bugs such as NLog not shutting down
(http://nlog-project.org/2011/10/30/using-nlog-with-mono.html).
[monodoc] Cleanups
[monodoc] Parse and display mastersummary.xml on root:/ ECMA urls
Remove dependency on generated file
Remove MonoTouch specific code that is now handled without reflection
Implement OP_LCONV_TO_I4 using OP_SEXT_I4 instead of OP_LSHR_IMM(0). Fixes #11058.
[xbuild] It's safe to pass /debug:pdbonly to mcs now
Misc .NET 4.5 / PCL APIs.
Add System.IO.Compression.FileSystem stubs.
HttpWebRequest/Response API fixes for .NET 4.5.
Missing WebUtility methods.
Trivial API additions.
Add System.Text.RegularExpressions.Regex timeout APIs.
System.Progress
BigInteger.Parse/TryParse() overloads for .NET 4.0.
System.Runtime.Serialization.DateTimeFormat
Add stubs for some new .NET 4.0/4.5 WCF APIs.
Merge pull request #505 from roji/shutdown_flow

Fixed threadpool+ProcessExit problem in shutdown flow
Small cleanup on runtime shutdown to move more code to the same spot and reduce duplication.