Remove pointless #elif branch in mono-membar.h.
Fix handling of the `volatile.` prefix instruction.

* Respect the `volatile.` prefix on all instructions specified in
  Ecma 335, Partition III, 2.6.
* Emit release barriers _before_ the instructions they affect.
* Skip certain optimizations when the `volatile.` prefix is used,
  since we can't easily emit barriers correctly in those
  optimization paths.
* Use `ins_flag` to check for `MONO_INST_VOLATILE` as it doesn't
  depend on an instruction having been emitted. This would kind of
  not work when we need to emit barriers before other instructions.
* Set `ins_flag` to zero in all cases where it's consumed.
[llvm] Fix llvm loading.
Ignore scripts/ikdasm.
[llvm] Fix a few problems with longs on 32 bit platforms. Fixes #18925.
xml type parameters have no size specifier

generate "@p1 xml" instead of "@p1 xml(123)"
Fix the date time set in file by removing the ':'.

This is the same code than the one under SendCore. The date time should
not have the : (time zone offset) to be able to use the file.
Added contribution guideline links in README 

New section has links to guideline wiki page, and the page's Important Rules section that all contributors should be aware of.
Merge pull request #987 from StephenMcConnel/bug-18874

Adjust scrollbar display after layout if autosized children
Add ICscHostObject4 skeleton
[windows] Remove sdb symbol from mono.def. Fix the build.
[VS] Change the tools version back to v110 so it works with VS 2012.
[windows] Win64 requires 16 bytes alignment too.
[runtime] Don't g_string_append an empty string when running regression tests.
[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