[MSBuild] Fixed a test that failed when the GAC wasn't available

Some types are statically known to never lead to a bridge. Objects like
string or int[]. By filtering them out very early in dfs1 we save memory by
not inserting them into the hashtable and reduce work done by all further steps.

This is currently breaking the build for Mono Droid.

This reverts commit bb3f24e9.

This is currently breaking the build for Mono Droid.

This reverts commit b175675a.

Otherwise parallel builds will break randomly.

Fix 'make check' when mono is not installed

Allow .NET 4.0 + users to use the ConnectSocket property

The bridge implementation can be picked by having bridge-implementation=old|new in
MONO_GC_PARAMS.

This commit just prepared the ground to land experimental improvements to the bridge
while retaining an working implementation by default.

This change is in preparation to introduce two implementations of the bridge.

The current implementation is now know as old.

SGEN_TV_GETTIME reports via mono_100ns_ticks(), but we treated the
values as if they were in us.

The changes are documented in the Xamarin.txt file.

When the xbuild_12 profile is verified, the corlib from the net_4_5
profile should be in the MONO_PATH, otherwise the verification will
fail with:

The assembly mscorlib.dll was not found or could not be loaded.
It should have been installed in the `.../mono/4.5/mscorlib.dll' directory.

This reverts commit 164f9cbe.

This reverts commit 9dd632fb, reversing
changes made to 164f9cbe.

This makes it easier to grab&use the version elsewhere in the future (e.g. in packaging)

Correctly apply DST offset if the date being converted falls after Jan 1st and is within the last year's DST zone

The adjustment rule must take into account that DST can start in the previous year and extend to some initial period
of the DateTime's year. This patch makes the code take that into account and correctly applies the DST offset to the
date being converted to some target timezone.

Fixes xambug https://bugzilla.xamarin.com/show_bug.cgi?id=17155

This reverts commit 5699e87d.

We don't disable tests that reveal regressions. This is one of such cases.

    * ConvertTime (DateTime, TimeZoneInfo) now correctly takes the date kind from the DateTime parameter
      and uses it to select the source time zone according to this criteria:

         if DateTime kind is Utc, use TimeZoneInfo.Utc as source, in all other cases use TimeZoneInfo.Local

    * Move argument checks in ConvertTime (DateTime, TimeZoneInfo, TimeZoneInfo) so that there's no risk of a NREX
      should sourceTimeZone be null.

Added relevant tests for all of the above changes.

Otherwise this happens:

    MCS     [monotouch] Mono.CSharp.dll
    ../../mcs/codegen.cs(294,7): error CS1061: Type `System.Reflection.Emit.ILGenerator' does not contain
    a definition for `BeginExceptFilterBlock' and no extension method `BeginExceptFilterBlock' of
    type `System.Reflection.Emit.ILGenerator' could be found. Are you missing an assembly reference?

Disable bug-18026.exe when running tests in the CI environment

The test performed in bug-18026.exe can sometimes fail if the hazard
table gets full. Disabling it in CI testing avoids unwanted noise.

See https://bugzilla.xamarin.com/show_bug.cgi?id=19235