AllowPartiallyTrustedCallers attribute missed after merge

[RusKnyaz]

Assemblies initialiy compiled with [assembly: AllowPartiallyTrustedCallers] lost this attribute after merge.
Steps to reproduce:

1. Create new class library project (targetFramework: 3.5)
2. Add line "[assembly: AllowPartiallyTrustedCallers]" to AssembliInfo.cs
3. Call ILMerge by "Ilmerge /out:out.dll ClassLibrary1.dll /targetplatform:v2" command
4. open out.dll in ILSpy or Reflector or any other tool
   Observed: there is no 'AllowPartiallyTrustedCallers' assembly attribute
   Expected: AllowPartiallyTrustedCallers attribute should be specified for the assembly (like in original ClassLibrary1.dll).

[cwellsx]

I found the source code which implements this restriction (it's easy to find), and posted on StackOverflow to ask why this restriction was introduced into the code -- Why does ILMerge delete security-related attributes?