use restrict everywhere it's required by c99 and/or posix 2008

to deal with the fact that the public headers may be used with pre-c99
compilers, __restrict is used in place of restrict, and defined
appropriately for any supported compiler. we also avoid the form
[restrict] since older versions of gcc rejected it due to a bug in the
original c99 standard, and instead use the form *restrict.

src/stat/fstatat.c

@@ -2,7 +2,7 @@
 #include "syscall.h"
 #include "libc.h"
 
-int fstatat(int fd, const char *path, struct stat *buf, int flag)
+int fstatat(int fd, const char *restrict path, struct stat *restrict buf, int flag)
 {
 	return syscall(SYS_fstatat, fd, path, buf, flag);
 }

src/stat/lstat.c

@@ -2,7 +2,7 @@
 #include "syscall.h"
 #include "libc.h"
 
-int lstat(const char *path, struct stat *buf)
+int lstat(const char *restrict path, struct stat *restrict buf)
 {
 	return syscall(SYS_lstat, path, buf);
 }

src/stat/stat.c

@@ -2,7 +2,7 @@
 #include "syscall.h"
 #include "libc.h"
 
-int stat(const char *path, struct stat *buf)
+int stat(const char *restrict path, struct stat *restrict buf)
 {
 	return syscall(SYS_stat, path, buf);
 }

src/stat/statvfs.c

@@ -39,7 +39,7 @@ static void fixup(struct statvfs *out, const struct statfs *in)
 	out->f_namemax = in->f_namelen;
 }
 
-int statvfs(const char *path, struct statvfs *buf)
+int statvfs(const char *restrict path, struct statvfs *restrict buf)
 {
 	struct statfs kbuf;
 	if (__statfs(path, &kbuf)<0) return -1;