vchoi_fork

[svn-r13047] Description:
    Add "attribute exists" internal routine to make verifying that an attribute
with the same name doesn't already exist easier.

    Tweak "trace" script to produce more whitespace in H5TRACE macros, in order
to make them easier to read.

    Minor other whitespace cleanups

Tested on:
    Linux/32 2.6 (chicago)
    Linux/64 2.6 (chicago2)