[RenderScript] Support tracking and dumping reduction kernels

Initial implementation of support for tracking
[RenderScript Reductions](https://developer.android.com/guide/topics/renderscript/compute.html#reduction-in-depth)

With this patch, `language renderscript module dump` properly lists reductions
that are part of loaded RenderScript modules as well the the consituent
functions and their roles, within the reduction.

This support required new tracking mechanisms for the `#pragma(reduce)`
mechanism, and extension of `RSModuleDescriptor::ParseRSInfo` to support
the metadata output by `bcc`. This work was also an opportunity to
refactor/improve parse code:

- `RSModuleDescriptor::ParseExportReduceCount` now has a complete
  implementation and the debugger can correctly track reductions on
  receipt of a module hook.
- `RSModuleDescriptor::Dump` now dumps Reductions as well as `ForEach`
  kernels. Also, fixed indentation of the output, and made indentation
  groupings in the source clearer.
- `RSModuleDescriptor::ParseRSInfo` now returns true if the `".rs.info"`
  packet has nonzero linecount, rather than rejecting RenderScripts that
  don't contain kernels (an unlikely situation, but possibly valid). This
  was changed because scripts that only contained reductions were not
  being tracked in `RenderScriptRuntime::LoadModule`.
- Refactor `RSModuleInfo::ParseRSInfo` and add reduction spec parser stub
 - Prepared ParseRSInfo to more easily be able to add new parser types
 - Use llvm::StringRef and llvm::StringMap helpers to make the parsing code cleaner
 - factor out forEachCount, globalVarCount, and pragmaCount parsing block to their own methods
 - Add ExportReduceCount Parser
 - Use `llvm::StringRef` in `RSKernelDescriptor` constructor
 - removed now superfluous `MAXLINE` macros as we've switched from `const
   char *` to `llvm::StringRef`

llvm-svn: 281717