This fixes a bug where the verifier was complaining about empty
accelerator tables. When the table is empty, its size is not a valid
offset as it points after the end of the section.
This patch also makes the extractor return llvm:Error instead of bool
for better error reporting in the verifier.
Differential revision: https://reviews.llvm.org/D41063
rdar://35932007
llvm-svn: 320399
ba915897da