GCC warnings on breakage of strict-aliasing rules

The branch CR24252 is created.

Violation of strict aliasing rules can lead to undefined behaviour when optimization mode is -O2 or higher.
One of possible solutions is usage of union to reference to an object using different types.

Please read
http://www.cyberforum.ru/c/thread802307.html
http://dbp-consulting.com/tutorials/StrictAliasing.html
http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html

The patch is reviewed; the part which consists in elimination of unnecessary type casts is pushed to branch CR24252_extract; please test. Other remaining problems will be registered as separate issues.

Dear Commenter 1,

Branch CR24252_extract (and products from GIT master) was compiled on Linux and Windows platforms and tested.
[revision removed]

Number of compiler warnings:

occt component :
Linux: 38 (55 on master)
Windows: 1 (1 on master)

products component :
Linux: 12 (20 on master)
Windows: 2 (2 on master)

Regressions/Differences:
No regressions/differences

Testing cases:
Not needed

Testing on Linux:
Total MEMORY difference: 358283328 / 357072508
Total CPU difference: 44045.470000000154 / 42990.139999999854

Testing on Windows:
Total MEMORY difference: 409959504 / 412885964
Total CPU difference: 29722.703125 / 31989.96875

There are not differences in images found by testdiff.