[runtime] Add some low level locks to image sets to reduce contention and the usage of the loader lock.
[jit] Rewrite lookup_method () to reduce contention by not taking the loader lock while doing hashtable lookups.
[System] handle arguments whose ToString returns null in String.Format

When an argument to String.Format has no formatter, its ToString method
is called. This change takes care that the FormatHelper can handle
arguments whose ToString() method returns null.
Merge pull request #996 from DavidS/fixes/string-format-nre

[System] handle arguments whose ToString returns null in String.Format
[mcs] Primary constructors
[mcs] Initial implemntation of exception filters
Update error message
Update tests
Make all Python scripts Python 3-friendly.
Add initial .travis.yml.
Only build master for now.
Avoid `make distcheck` in .travis.yml for now.
Fall back to calling Java.Util.TimeZone.Default.ID if the persist.sys.timezone system
property is not present on the system or its value is an empty string. This ensures that
we obtain valid timezone info on systems which do not define the above property.

Part of fix for https://bugzilla.xamarin.com/show_bug.cgi?id=4902
[mcs] Emit exception filters with empty stack
[llvm] Fix the loadable llvm build.
[win64] Fix stack probing and disable omit_fp. Fixes iltests.

Stack probing on windows must be done a page a time so we must always force it to happen on windows.
Disable omit_fp on win64 for now as it makes the tail call tests fail.
[jit] Fix the lookup of the AOT version of Interlocked.Exchange<T> in full-aot mode. Fixes #19070.
Remove empty space from assembly name
Update the configuration file for project builds
Runtime documentation will now build with srcdir != builddir

This removes an old and broken patch that did not allow for
clean builds of Mono.   The old patch was so bad, that instead
of fixing the actual source of the problem (the ability to build
the runtime documentation when the source directory was not the
same as the build directory), a hack was added to circumvent
`make distcheck''s security system and changed the permissions
at build time for the source directory to become read/write.

This fixes the problem