Allow programs to use include files from SDCC like stdint.h and stdbool

[aoineko-fr]

Problem is SDCC and MSXgl lib conflict on some headers name (math.h and string.h). That said, as I'm adding the /tools/ directory to the include directories, you can already include the SDCC standard lib headers with, for example: #include "sdcc/include/stdint.h".

[pvmm]

Since MSXgl is the non-standard library, maybe it should reside in a different namespace (directory). I fixed it in my project_config.js and I will leave this here since it could be useful:

//-- Additionnal compilation options (string)
CompileOpt = `-I${RootDir}tools/sdcc/include/`;