Add configure script

Get rid of all the fragile guessing and checking of features,
and roll a configure script instead.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/helpers.c b/helpers.c
index 1b4e1d0..dce967d 100644
--- a/helpers.c
+++ b/helpers.c
@@ -9,50 +9,31 @@
 #include "arch/arch.h"
 #include "os/os.h"
 
-#ifndef FIO_HAVE_LINUX_FALLOCATE 
-int _weak fallocate(int fd, int mode, off_t offset, off_t len)
+#ifndef CONFIG_LINUX_FALLOCATE
+int fallocate(int fd, int mode, off_t offset, off_t len)
 {
 	errno = ENOSYS;
 	return -1;
 }
 #endif
 
-#ifndef __NR_fallocate
-int _weak posix_fallocate(int fd, off_t offset, off_t len)
+#ifndef CONFIG_POSIX_FALLOCATE
+int posix_fallocate(int fd, off_t offset, off_t len)
 {
 	return 0;
 }
 #endif
 
-int _weak inet_aton(const char *cp, struct in_addr *inp)
-{
-	return 0;
-}
-
-int _weak clock_gettime(clockid_t clk_id, struct timespec *ts)
-{
-	struct timeval tv;
-	int ret;
-
-	ret = gettimeofday(&tv, NULL);
-
-	ts->tv_sec = tv.tv_sec;
-	ts->tv_nsec = tv.tv_usec * 1000;
-
-	return ret;
-}
-
-#ifndef __NR_sync_file_range
-int _weak sync_file_range(int fd, off64_t offset, off64_t nbytes,
-			   unsigned int flags)
+#ifndef CONFIG_SYNC_FILE_RANGE
+int sync_file_range(int fd, off64_t offset, off64_t nbytes, unsigned int flags)
 {
 	errno = ENOSYS;
 	return -1;
 }
 #endif
 
-#ifndef FIO_HAVE_FADVISE
-int _weak posix_fadvise(int fd, off_t offset, off_t len, int advice)
+#ifndef CONFIG_FADVISE
+int posix_fadvise(int fd, off_t offset, off_t len, int advice)
 {
 	return 0;
 }