Adding autogenerated Ceres config.h to #define Ceres compile options.

- Previously we passed all compile options to Ceres via add_definitions
  in CMake.  This was fine for private definitions (used only by Ceres)
  but required additional work for public definitions to ensure they
  were correctly propagated to clients via CMake using
  target_compile_definitions() (>= 2.8.11) or add_definitions().
- A drawback to these approaches is that they did not work for chained
  dependencies on Ceres, as in if in the users project B <- A <- Ceres,
  then although the required Ceres public compile definitions would
  be used when compiling A, they would not be propagated to B.

- This patch replaces the addition of compile definitions via
  add_definitions() with an autogenerated config.h header which
  is installed with Ceres and defines all of the enabled Ceres compile
  options.
- This removes the need for the user to propagate any compile
  definitions in their projects, and additionally allows post-install
  inspect of the options with which Ceres was compiled.

Change-Id: Idbdb6abdad0eb31e7540370e301afe87a07f2260

internal/ceres/generated/partitioned_matrix_view_2_4_9.cc

diff --git a/internal/ceres/generated/partitioned_matrix_view_2_4_9.cc b/internal/ceres/generated/partitioned_matrix_view_2_4_9.cc
index 8fea0bd..d853860 100644
--- a/internal/ceres/generated/partitioned_matrix_view_2_4_9.cc
+++ b/internal/ceres/generated/partitioned_matrix_view_2_4_9.cc
@@ -40,6 +40,9 @@
 // This file is generated using generate_partitioned_matrix_view_specializations.py.
 // Editing it manually is not recommended.
 
+// This include must come before any #ifndef check on Ceres compile options.
+#include "ceres/internal/port.h"
+
 #ifndef CERES_RESTRICT_SCHUR_SPECIALIZATION
 
 #include "ceres/partitioned_matrix_view_impl.h"