Refactor msb check and emittion

[taichi-ishitani]

This PR is to fix following two issues of msb feature.

• msb cannot be used on struct/union member, enum and paramter
• Wrong msb position calcuration for a type defined in outside of the current scope
  • resolving msb of struct member is failed #1142 (comment)
  • use $size and $bits system function instead of evaluating the size declaration

fix #1142