libc - Porting libc from C to Go

This is a subproject of the c2go project.

What's our plan?

First, port printf and its dependent C functions to Go. Stage: Almost Done, see supported C standard libary types/functions/variables.
Second, support libc in the Go+ language. Stage: Done, see how Go+ interacts with C.
Third, port musl libc-test project to Go. Stage: Doing, see ported test cases.
Fourth, port all sqlite3 dependent C functions. Stage: Planning, see sqlite3 dependent fuctions.
Last, support most of C standard library functions and can import them by Go+. Stage: Planning.