Pull request: server/util_md5.c:58 - replace magic number with constant arithmetic

[SiPlus]

Hello, dev@.

I request a little change to HTTPD code.
On line 58 of server/util_md5.c, please replace

char  *r,  result[33];  /* (MD5_DIGESTSIZE * 2) + 1 */

with

char  *r,  result[2*APR_MD5_DIGESTSIZE+1];

There's only constant arithmetic here, so I don't see a reason to 
pre-calculate the size here, and other code files use 
2*APR_MD5_DIGESTSIZE+1 often.

Thanks,
SiPlus