Changes

[test] Properly test -Werror-implicit-function-declaration and -Wvec-elem-size

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D90874

Check for nullptr before dereferencing in translateModuleToLLVMIR()

This is defensive with respect to invocations of this API with an IR
that isn't ready to be converted to LLVM IR.

[BranchProbabilityInfo] Get rid of MaxSuccIdx. NFC

This refactoring allows to eliminate the MaxSuccIdx map
proposed in the commit a7b662d0.
The idea is to remove probabilities for a block BB for
all its successors one by one from first, second, ...
till N-th until they are defined in Probs. This works
because probabilities for the block are set at once for
all its successors from number 0 to N-1 and the rest
are removed if there were stale probs.
The protected method setEdgeProbability(), which set
probabilities for individual successor, is removed.
This makes it clear that the probabilities are set in
bulk by the public method with the same name.

Reviewed By: kazu, MaskRay

Differential Revision: https://reviews.llvm.org/D90837

[mlir][CAPI] Add missing 'static' to inline C function.

* Asked to submit separately from https://reviews.llvm.org/D90824