The "normal" ISO date/time includes a T between date and time. It also
allows dropping the colons and seconds from the timespec. Add new
patterns for these forms as well as tests.
Prior to this patch, DST times where tested by specifying a custom TZ
environment variable that didn't defined DST transition times.
Due to a bug in glibc, the test fail on 32bits platforms that use timezone
files generated by zic from tzcode >= 2014c (glibc >= 2.20).
See https://sourceware.org/bugzilla/show_bug.cgi?id=19738
By defining explicit transition times for DST in the TZ environment variable,
the test is now independant to how the system guess those transition times.
Adding support to parsedate in util module to understand the more idiomatic
dates 'today' and 'yesterday'.
Added unified tests and docstring tests for added functionality.
The use of "{datetime}" was unfortunate since I as a user never knew
if I was expected to do
hg log -d '>{2011-04-01}'
or
hg log -d '>2011-04-01'
The word "datetime" is also confusing -- calling it a date it much
simpler.
