Rewrite DSAA::getModRefInfo to compute the mapping between caller and callee to determine mod/ref behavior, instead of creating a *copy* of the caller graph and inlining the callee graph into the copy.
Rewrite DSAA::getModRefInfo to compute the mapping between caller and callee
to determine mod/ref behavior, instead of creating a *copy* of the caller
graph and inlining the callee graph into the copy.

This speeds up aa-eval on Ptrdist/yacr2 from 109.13s to 3.98s, and gives
identical results.  The speedup is similar on other programs.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@20669 91177308-0d34-0410-b5e6-96231b3b80d8

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