Writing a table generator
 
 This documentation is preliminary.
 Parts of the API are not good and should be changed.
 
 Basic concepts
 
 A table generator consists of two files, *_tablegen.c and *_tablegen.h.
 The .h file will provide the variable declarations and initialization

 code for the tables, the .c calls the initialization code and then prints
 the tables as a header file using the tableprint.h helpers.

 Both of these files will be compiled for the host system, so to avoid
 breakage with cross-compilation neither of them may include, directly
 or indirectly, config.h or avconfig.h.

 This means that e.g. libavutil/mathematics.h is ok but libavutil/libm.h is not.

 Due to this, the .c file or Makefile may have to provide additional defines
 or stubs, though if possible this should be avoided.

 In particular, CONFIG_HARDCODED_TABLES should always be defined to 0.

 
 The .c file
 
 This file should include the *_tablegen.h and tableprint.h files and
 anything else it needs as long as it does not depend on config.h or
 avconfig.h.

 In addition to that it must contain a main() function which initializes
 all tables by calling the init functions from the .h file and then prints
 them.
 The printing code typically looks like this:
     write_fileheader();
     printf("static const uint8_t my_array[100] = {\n");

     write_uint8_t_array(my_array, 100);

     printf("};\n");
 

 This is the more generic form, in case you need to do something special.
 Usually you should instead use the short form:
     write_fileheader();
     WRITE_ARRAY("static const", uint8_t, my_array);
 

 write_fileheader() adds some minor things like a "this is a generated file"
 comment and some standard includes.
 tablegen.h defines some write functions for one- and two-dimensional arrays
 for standard types - they print only the "core" parts so they are easier
 to reuse for multi-dimensional arrays so the outermost {} must be printed
 separately.
 If there's no standard function for printing the type you need, the
 WRITE_1D_FUNC_ARGV macro is a very quick way to create one.
 See libavcodec/dv_tablegen.c for an example.
 

 
 The .h file
 
 This file should contain:
  - one or more initialization functions
  - the table variable declarations
 If CONFIG_HARDCODED_TABLES is set, the initialization functions should
 not do anything, and instead of the variable declarations the
 generated *_tables.h file should be included.
 Since that will be generated in the build directory, the path must be
 included, i.e.
 #include "libavcodec/example_tables.h"
 not
 #include "example_tables.h"
 
 Makefile changes
 
 To make the automatic table creation work, you must manually declare the
 new dependency.
 For this add a line similar to this:
 $(SUBDIR)example.o: $(SUBDIR)example_tables.h
 under the "ifdef CONFIG_HARDCODED_TABLES" section in the Makefile.