some std wrappers around libc

examples/brainfuck.zr

@@ -1,7 +1,7 @@
 func main[] : I64
     // https://brainfuck.org/sierpinski.b
     let src: String = "++++++++[>+>++++<<-]>++>>+<[-[>>+<<-]+>>]>+[-<<<[->[+[-]+>++>>>-<<]<[<]>>++++++[<<+++++>>-]+<<++.[-]<<]>.>+[>>]>+]"
-    let src_len: I64 = c.strlen(src)
+    let src_len: I64 = str.len(src)
     let i: I64 = 0
 
     let memory: Ptr = c.calloc(1, 30000)
@@ -45,4 +45,4 @@ func main[] : I64
 
         i = i + 1
 
-    c.free(memory)
+    mem.free(memory)