Fix warnings reported by VS 2015

[DickvdBrink]

Fix warnings reported by VS 2015 - blocks #3862

In total there are currently 2085 warnings but some of them are reported multiple times on the same location so it is not that bad :)

We can also disable them but that might not be wise (at least not for all of them :))

Could not find a msdn link for this one
Warning C4463 overflow; assigning 1 to bit-field that can only hold values from -1 to 0

metamodelrw.cpp#L2755
metamodelrw.cpp#L3173
metamodelrw.cpp#L3359

Warning C4312
This warning detects an attempt to assign a 32-bit value to a 64-bit pointer type, for example, casting a 32-bit int or long to a 64-bit pointer

To much of this one to list but some of them:
'<function-style-cast>': conversion from 'const int' to 'IMDInternalImport *' of greater size cee_dac
holder.h#L659

And similar

Warning C4311
This warning detects 64-bit pointer truncation issues. For example, if code is compiled for a 64-bit architecture, the value of a pointer (64 bits) will be truncated if it is assigned to an int (32 bits). For more information
simplerhash.h#L450

Warning C4302
The compiler detected a conversion from a larger type to a smaller type. Information may be lost
simplerhash.h#L450

[jkotas]

I will take care of these.