Move C standard library pxd files to libc package

--HG--
rename : Cython/Includes/stdio.pxd => Cython/Includes/libc/stdio.pxd
rename : Cython/Includes/stdlib.pxd => Cython/Includes/libc/stdlib.pxd

Cython/Includes/libc/__init__.pyx

+# empty file

Cython/Includes/libc/stdio.pxd

+cdef extern from "stdio.h" nogil:
+    ctypedef struct FILE
+    int printf(char *format, ...)
+    int fprintf(FILE *stream, char *format, ...)
+    int sprintf(char *str, char *format, ...)
+    FILE *fopen(char *path, char *mode)
+    int fclose(FILE *strea)
+    cdef FILE *stdout
+    int scanf(char *format, ...)

Cython/Includes/libc/stdlib.pxd

+
+cdef extern from "stdlib.h" nogil:
+    void free(void *ptr)
+    void *malloc(size_t size)
+    void *realloc(void *ptr, size_t size)
+    size_t strlen(char *s)
+    char *strcpy(char *dest, char *src)

Cython/Includes/stdio.pxd

-cdef extern from "stdio.h" nogil:
-    ctypedef struct FILE
-    int printf(char *format, ...)
-    int fprintf(FILE *stream, char *format, ...)
-    int sprintf(char *str, char *format, ...)
-    FILE *fopen(char *path, char *mode)
-    int fclose(FILE *strea)
-    cdef FILE *stdout
-    int scanf(char *format, ...)
+# Present for backwards compatability
+from libc.stdio cimport *

Cython/Includes/stdlib.pxd

-
-cdef extern from "stdlib.h" nogil:
-    void free(void *ptr)
-    void *malloc(size_t size)
-    void *realloc(void *ptr, size_t size)
-    size_t strlen(char *s)
-    char *strcpy(char *dest, char *src)
+# Present for backwards compatability
+from libc.stdlib cimport *

tests/run/libc_stdlib.pyx

+"""
+>>> f()
+'hello'
+"""
+
+from libc.stdio cimport sprintf
+
+def f():
+    cdef char buf[10]
+    sprintf(buf, b'hello')
+    return str((<object>buf).decode('ASCII'))