Add minimal library to be imported into Sparrow

[lucteo]

Very minimal library: one header + one C source file

min.h:
int min(int a, int b);

min.c:
int min(int a, int b) {
return a<b ? a : b;
}

Add a makefile that creates a static library (libmin.a) our of the given files.

This will be used as a working library of C code to import.