[analyzer] Add new PreImplicitCall and PostImplicitCall ProgramPoints.

These are currently unused, but are intended to be used in lieu of PreStmt
and PostStmt when the call is implicit (e.g. an automatic object destructor).

This also modifies the Data1 field of ProgramPoints to allow storing any
pointer-sized value, as opposed to only aligned pointers. This is necessary
to store SourceLocations.

There is currently no BugReporter support for these; they should be skipped
over in any diagnostic output.

This commit also tags checkers that currently rely on function calls only
occurring at StmtPoints.

llvm-svn: 160019