Implement `analysis_preludes`/generate function prologues

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We should generate possible function preludes and check for them by implementing RzAnalysisPluging.preludes:

static RzList /*<RzSearchKeyword *>*/ *analysis_preludes(RzAnalysis *analysis);

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The prologue generation in LLVM is implemented in void HexagonFrameLowering::insertPrologueInBlock. But there should be other information about it in HexagonFrameLowering.cpp