libroot_build & fs_shell: Provide _kern_ functions for readv/writev...

..instead of readv_pos/writev_pos. This way, we can be sure that we
are remapping them properly even under Haiku, as well as remove some
potential confusions.

bfs_shell seems to still work fine on a regular build.

headers/build/BeOSBuildCompatibility.h

@@ -48,10 +48,6 @@ extern size_t	strnlen(const char* string, size_t length);
 #if !defined(HAIKU_HOST_PLATFORM_HAIKU)
 extern ssize_t  read_pos(int fd, off_t pos, void* buffer, size_t count);
 extern ssize_t  write_pos(int fd, off_t pos, const void* buffer, size_t count);
-extern ssize_t	readv_pos(int fd, off_t pos, const struct iovec* vec,
-					int count);
-extern ssize_t	writev_pos(int fd, off_t pos, const struct iovec* vec,
-					int count);
 #endif
 
 

headers/build/private/kernel/syscalls.h

@@ -35,7 +35,9 @@ extern "C" {
 #define _kern_remove_attr			_kernbuild_remove_attr
 #define _kern_rename_attr			_kernbuild_rename_attr
 #define _kern_read					_kernbuild_read
+#define _kern_readv					_kernbuild_readv
 #define _kern_write					_kernbuild_write
+#define _kern_writev				_kernbuild_writev
 #define _kern_read_dir				_kernbuild_read_dir
 #define _kern_rewind_dir			_kernbuild_rewind_dir
 #define _kern_read_stat				_kernbuild_read_stat
@@ -80,8 +82,12 @@ extern status_t		_kern_rename_attr(int fromFile, const char *fromName,
 // file descriptor functions
 extern ssize_t		_kern_read(int fd, off_t pos, void *buffer,
 						size_t bufferSize);
+extern ssize_t		_kern_readv(int fd, off_t pos, const struct iovec *vecs,
+						size_t count);
 extern ssize_t		_kern_write(int fd, off_t pos, const void *buffer,
 						size_t bufferSize);
+extern ssize_t		_kern_writev(int fd, off_t pos, const struct iovec *vecs,
+						size_t count);
 extern ssize_t		_kern_read_dir(int fd, struct dirent *buffer,
 						size_t bufferSize, uint32 maxCount);
 extern status_t		_kern_rewind_dir(int fd);