ap_uuencode was not allocating space for terminating '\0'

ap_uudecode was running past the beginning of the buffer for empty input
strings, and past the end of the buffer for certain (invalid) input

PR: 3422
Reviewed by:	Dean Gaudet


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@83048 13f79535-47bb-0310-9956-ffa450edef68