* in 1.3: Changed types used in rrd_file_t from off_t to size_t to prevent: warning...

* in 1.3: Changed types used in rrd_file_t from off_t to size_t to prevent: warning: comparison between signed and unsigned
* Misc other off_t -> size_t changes to prevent signed warning
* in 1.3: Added rrd_dump_opt_r declaration to prevent undef warning
* Explicit cast to time_t of check in rrd_fetch to prevent signed warning
* Added vasprintf path to sprintf_alloc to prevent excessive mallocing
* in 1.3: fixed STRERROR_R_CHAR_P undef warning

patch by Steven Hartland killing multiplay.co.uk

git-svn-id: svn://svn.oetiker.ch/rrdtool/branches/1.3@1808 a5681a0c-68f1-0310-ab6d-d61299d08faa