Blender Git Loki

Partially revert ef3eb7adc6f283145e28781a05b3b5e73a6cf083

The .exe extension *is* needed on Windows for makesrna, contray to the
patch author's protestations otherwise. Omitting it breaks compilation
on mingw at least (i.e. "rename()" fails). Thanks to "PerfectionCat"
for narrowing down this bug.

makesdna on the other hand still seems to work ok from a quick test I did.
Unless more issues crop up, just reverting this part of the patch should
be ok, though IMO these changes were unnecessary in the first place.