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

The test tried to resolve an assembly from the GAC, which doesn't work on a
clean machine without an existing Mono installation.
We now check if the GAC directory is missing and ignore the test in that case.
[Sys.Data] Add unit tests for Novell bug #519648

These unit tests demonstrate the difference to .NET
(https://bugzilla.novell.com/show_bug.cgi?id=519648).
[Sys.Data] Fix Novell Bug #519648

Don't throw an exception when passing "new object[] {null}" to
DataRowCollection.Find. This makes the behaviour more compatible
with .NET. This fixes bug #519648
(https://bugzilla.novell.com/show_bug.cgi?id=519648).
[System.XML] Add unit test for #18118
[System.XML] Fix handling of global variables in XSLs (#18118)
[System.XML] Add unit test for XSL note-set bug (#18114)
[System.XML] Fix XSL node-set bug (#18114)

XSL node-set function now behaves more like MS version.
[System.XML] Add unit test for XSL value-of bug (#18113)
[System.XML] Fix handling of space in XSL value-of elements (#18113)
[mcs] Adding unit test for #18511
[mcs] Fix recursive resolving of crefs (#18511)
[Fix] Bugzilla #18213 - System.Runtime.Caching.MemoryCache doesn't honor SlidingExpiration
xml type parameters have no size specifier

generate "@p1 xml" instead of "@p1 xml(123)"
[Mono.Debugger.Soft] Throw a NotSupportedException if we encounter an unsupported IL opcode
[Http]: Correctly handle request bodies when resending with authentication.

My previous changes modified the way how we're handing the request body when
resending a request due to a 30x redirection.

Authentication is a "special" form of redirection because we sometimes need
to resend a request with additional authentication headers.  Unfortunately,
I forgot this, causing a regression which is now fixed.

This has been reported as bugs #19119 and #19068.
Really, seriously, for real fix mono/tests/Makefile.am when run with CI=1/V=1.
[sgen-bridge] Introduce accounting mode to bridge processing.

This accounting mode logs the "cost" of each bridge-object during bridge processing.
This should give a very good first clue on how expensive each object is.
[genproj] Some hygiene changes to genproj, to be able to even digest this
Hopefully fix a build error in libgc on some compilers.

../../libgc/alloc.c: In function ‘GC_stopped_mark’:
../../libgc/alloc.c:501:9: error: implicit declaration of function ‘GC_cond_register_dynamic_libraries’ [-Werror=implicit-function-declaration]
         GC_cond_register_dynamic_libraries();
Fix my last commit to match our libgc's declaration style.