Generate .c for .y and .l

- For .l/.y source files, generate .c files; for .ll/.yy source files,
  generate c++ files.
- Simplified the rules by adding the generated sources to
  my_generated_sources.
- Simplified generated header file naming by always using .h extension
  with bison's "--defines=" option.
- Removed the unnecesarry conditional inclusion to the generated
  headers. Bison already automatically generates such things.

Bug: 26492989
Change-Id: I9ab6dc149c258f7642bc36c3fa32f90ff7ee51a4