[ORC] Simplify naming for JITDylib definition generators.

Renames:
  JITDylib's setFallbackDefinitionGenerator method to setGenerator.
  DynamicLibraryFallbackGenerator class to DynamicLibrarySearchGenerator.
  ReexportsFallbackDefinitionGenerator to ReexportsGenerator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@344489 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed