Rename crc functions to private namespace

Apparently we overlap with some gtk (?) crc32() functions, causing
ours to be called and subsequently crashing since the arguments
aren't the same.

Move everything to a fio_ protected namespace.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/crc/md5.h b/crc/md5.h
index 6747d30..668f0e9 100644
--- a/crc/md5.h
+++ b/crc/md5.h
@@ -16,13 +16,13 @@
 #define MD5STEP(f, w, x, y, z, in, s) \
 	(w += f(x, y, z) + in, w = (w<<s | w>>(32-s)) + x)
 
-struct md5_ctx {
+struct fio_md5_ctx {
 	uint32_t *hash;
 	uint32_t block[MD5_BLOCK_WORDS];
 	uint64_t byte_count;
 };
 
-extern void md5_update(struct md5_ctx *, const uint8_t *, unsigned int);
-extern void md5_init(struct md5_ctx *);
+extern void fio_md5_update(struct fio_md5_ctx *, const uint8_t *, unsigned int);
+extern void fio_md5_init(struct fio_md5_ctx *);
 
 #endif