Refactor of DwarfDebug.cpp code.
Currently, collectCallSiteParameters method searches for instructions which load values into
registers used for parameters passing. Previously, interpretation of those values, loaded by one such
instruction, was implemented inside collectCallSiteParameters method.
This patch moves the interpretation code from collectCallSiteParameters method
into a separate static method named interpretValue. New method is called from
collectCallSiteParameters to process each instruction from targeted instruction scope.
Currently collectCallSiteParameters searches for loaded parameter value among instructions
which precede the call instruction, inside the same basic block.
When needed, new method (interpretValue) could be used for searching any instruction scope.
This is preparation for search of parameter value, loaded inside call delay slot.