related public APIs.
[base] Added a public API to change the levels of tracing components.
* src/base/ftdebug.c: Added new variables.
(ft_debug_init): Updates to support the change of levels of tracing
components of FreeType at run-time.
(FT_Trace_Set_Level): New function to change the levels of tracing
components at run-time.
(FT_Trace_Set_Default_Level): New function to reset the levels of
tracing components back to default.
* include/freetype/ftchapters.h: Added `debugging_apis' section under
`support_api' chapter.
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