Many MSVC warnings on type conversion, possible loss of data

[N-Dekker]

When all warnings are enabled (/Wall), VS2017 produces many warnings about "conversion from type to type, possible loss of data", during a Release build of elastix.

It appears that MSVC distinguishes three kind of "possible loss of data" warnings: C4242 C4244, and C4267.

The following table shows the number of warnings of each kind (number of distinct warnings, and total number of warnings of each kind):

C4242	43	1763	Warning level 4 (/Wall only)
C4244	93	145	Warning level 2
C4267	128	2425	Warning level 3

Sum:	264	4333

These warning might be related to Elastix crashes without any notice, reported by Philipp Heinrich.