parameters name in function declaration.
(FT_Custom_Log_Handler): Changed function name `ft_custom_log_handler'->
`FT_Custom_Log_Handler'.
Updated documentation.
* include/freetype/ftchapters.h: Added `debugging_apis' section under
`support_api' chapter.
* .gitmodules: Updated submodule to track recent changes in dlg library.
* src/base/ftdebug.c (ft_log_handler): Updated code according to the
recent updates in dlg library.
(ft_logging_init): Added environment variable `FT_LOGGING_FILE', the
variable `ft_fileptr' stores it's value.
Changed function name `ft_custom_log_handler'->
`FT_Custom_Log_Handler'.
* include/freetype/internal/ftdebug.h: Changed function name
`ft_custom_log_handler'-> `FT_Custom_Log_Handler'.
* README.git: Updated documentation.
* docs/DEBUG: Updated documentation.
Priyeshkkumar