ARM stopped supporting enabling of FP exceptions years ago.
Bug: http://b/68832485
Test: ran tests
Change-Id: I8450baa78e04d994c352180975b0a1ecd5a9f662
Factored out common declarations to include/fenv.h and pushed
the implementation to .c files.
Bug: 11050744
Change-Id: I446b13cc4bc599d328343a8d392b07de280f6304