loop.c: klibc specific fix for ioctl argument 3

Fixing:
| loop.c:20:14: error: too few arguments to function 'ioctl'
|   int devnr = ioctl(fd, LOOP_CTL_GET_FREE);
|               ^
| In file included from loop.c:6:0:
| /oe/oe-core/build/tmp-glibc/sysroots/poodle/usr/lib/klibc/include/unistd.h:111:14: note: declared here
|  __extern int ioctl(int, int, void *);
|               ^
| loop.c: In function 'losetup':
| loop.c:48:12: warning: passing argument 3 of 'ioctl' makes pointer from integer without a cast
|   int res = ioctl(loopfd, LOOP_SET_FD, filefd);
|             ^
| In file included from loop.c:6:0:
| /oe/oe-core/build/tmp-glibc/sysroots/poodle/usr/lib/klibc/include/unistd.h:111:14: note: expected 'void *' but argument is of type 'int'
|  __extern int ioctl(int, int, void *);
|               ^
| make: *** [loop.o] Error 1

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
mininit.c: klibc specific fix around missing setlinebuf

Klibc has buffered I/O since v. 2.0 but still lacks some streeam functions.

Fixing:
| mininit.o: In function `main':
| mininit.c:(.text.startup+0x70): undefined reference to `setlinebuf'

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
syspart.c: klibc specific fix for pivot_root syscall

Compiling against klibc we invoke directly the syscall
(generated into syscall stubs in their own files).
See /usr/klibc/SYSCALLS.def

Fixing:
| syspart.c: In function 'switch_root':
| syspart.c:26:2: warning: implicit declaration of function 'syscall' [-Wimplicit-function-declaration]
|   if (syscall(SYS_pivot_root, ".", "boot")) {
|   ^
| syspart.c:26:14: error: 'SYS_pivot_root' undeclared (first use in this function)
|   if (syscall(SYS_pivot_root, ".", "boot")) {
|               ^

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>