[analyzer] Don't add arrow to the inlined function's decl when it has no body.

In plist output mode with alternate path diagnostics, when entering a function,
we draw an arrow from the caller to the beginning of the callee's declaration.
Upon exiting, however, we draw the arrow from the last statement in the
callee function. The former makes little sense when the declaration is
not a definition, i.e. has no body, which may happen in case the body
is coming from a body farm, eg. Objective-C autosynthesized property accessor.

Differential Revision: https://reviews.llvm.org/D33671

llvm-svn: 304713