Other implementations of the symbol graph format use zero-based indices
for source locations, which causes problems when combined with clang's
current one-based indices. This commit sets ExtractAPI's symbol graph
output to use zero-based indices to align with other implementations.
rdar://107639783
getFragmentsForType resulted in a bool typeIdentifier fragment to be spelled "_Bool".
This fixes the spelling to be "bool" and checks it in C and C++.
Reviewed By: dang
Differential Revision: https://reviews.llvm.org/D158474