[LLDB] Use llvm::APInt and llvm::APFloat in Scalar and RegisterValue

Eliminated ENABLE_128_BIT_SUPPORT and union ValueData from Scalar.cpp and use llvm::APInt and llvm::APFloat for all integer and floating point types. Also used Scalar in RegisterValue.cpp

Reviewers: jaydeep, clayborg, jasonmolenda, ovyalov, emaste
Subscribers: tberghammer, ovyalov, emaste, mohit.bhakkad, nitesh.jain, bhushan
Differential: http://reviews.llvm.org/D10919
llvm-svn: 245216