Remove all references to int16.

Change-Id: Iab87463dd32f64ee371e6cc7d1f5e30128412a10

include/ceres/types.h

@@ -45,7 +45,6 @@ namespace ceres {
 
 // Basic integer types. These typedefs are in the Ceres namespace to avoid
 // conflicts with other packages having similar typedefs.
-typedef short int16;
 typedef int   int32;
 
 // Argument type used in interfaces that can optionally take ownership

internal/ceres/integral_types.h

@@ -77,7 +77,6 @@ struct UnsignedInteger {
 #undef CERES_INTSIZE
 
 typedef Integer< 8>::type int8;
-typedef Integer<16>::type int16;
 typedef Integer<32>::type int32;
 typedef Integer<64>::type int64;