Summary:
Add usage count to find-all-symbols.
FindAllSymbols now finds (most!) main-file usages of the discovered symbols.
The per-TU map output has NumUses=0 or 1 (only one use per file is counted).
The reducer aggregates these to find the number of files that use a symbol.
The NumOccurrences is now set to 1 in the mapper rather than being inferred by
the reducer, for consistency.
The idea here is to use NumUses for ranking: intuitively number of files that
use a symbol is more meaningful than number of files that include the header.
Reviewers: hokein, bkramer
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D30210
llvm-svn: 296446
Sam McCall