hdf5

[svn-r18212] Description:
    Bring revisions from Coverity fixing branch to trunk:

r18184:
Fixed Coverity issue 373.  Allocated memory freed in line 762 in case of error.

r18185:
Fixed Coverity issues 357 & 358.  Added check for NULL pointer before use.

r18186:
Fix coverity item 65.   Added code to h5unjam to correctly handle failures in
read() and write, and also to correctly handle writes that write less than
requested.

r18187:
Fix coverity items 115 and 116.   Added code to H5Tenum.c to correctly close
opened datatypes in case of failure.

r18188:
Fixed Coverity issue 46.  Check that dataset->shared is not null when freeing
memory after error.

r18190:
Fix coverity item 95.   Added code to H5T_create_vlen to correctly close
allocated datatype in case of failure.

r18191:
Fixed Coverity error 59.  Checked sfirst for -1 value before use in line 10533.

r18192:
Fix Coverity items 121 and 28

Added Asserts:
121: assert that all dimensions of count have values greater than zero.
28: assert curr_span pointer is not null before dereference.

Note: still need too add checks in hyperslab APIs that fail
     when count values are zero, and appropriate tests.

r18194:
Fixed Coverity issues 61 & 62. Checked variable snpoints for value < 0 in line
218.

Tested on:
    Mac OS X/32 10.6.2 (amazon) w/debug & production
    (already daily tested on coverity branch)