g++: types.h compilation warning -Wundef

[peterlauro1973]

when the api/mraa/types.h is included in include hierarchy of project which compiles with a warning flag -Wundef, the following warning is shown

/api/mraa/types.h:56:5:  warning: "__STDC_VERSION__" is not defined, evaluates to 0 [-Wundef]
   56 | #if __STDC_VERSION__ >= 199901L

instead of #if __STDC_VERSION__ >= 199901L
utilize: #if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L