Add the Mesh graph structure utility
fix the extern "C" problem:
my CPP code want call the function defined in .c
I can't include the C declaration header file cause the Cpp compile conversion didn't compatible with C for example Given a function defined in C void fool(int),
the C conversion may be foolint
while the cpp conversion may fool_int so when come to the link stage the cpp will not find the fool_int! Here come the problem can't find the symbol