Upgrade rails to 3.2.21
Be clearer on backslash usage.

See #4282
Fix #4414 & #4415 - exitfunc and proper null-terminated string

This patch fixes the following for messagebox.rb

Issue 1 (#4415)
When exitfunc is none, the payload will not be able to generate
due to an "invalid opcode" error.

Issue 2: (#4414)
After "user32.dll" is pushed onto the stack for the LoadLibrary
call, the payload does not actually ensure bl is a null byte, it
just assumes it is and uses it to modify the stack to get a
null-terminated string.

Fix #4414
Fix #4415
Define the Rails version constraint in a library constant
Fix jcxz to jecxz for x86_64 in metasm

This fixes "invalid opcode near 'jecxz'" for x64 metasm encoding.
Add new/updated r7 employees to mailmap
Add and sort other contributors in mailmap
Make the version constraint a range
Land #4434, fix for metasm invalid opcode
Lands #4429 by fixing windows/messagebox with EXITFUNC=none
Lands #4426 by cleaning up the module description
pull latest mdm
Land #4416, define rails version dep in one place

* Bump rails to 3.2.21
Land #4433 - Update mailmap
Lands #4436, latest version of MDM

Fixes an issue with protocol inclusion when adding an NX console
Updating lockfile post MDM version bump
Merge remote-tracking branch 'upstream/master'