Fix typo in ustring::find_last_not_of
Minor bug fix to timer -- apple didn't handle reversing order of times
maketx fixes -- fix making textures from source images that are crop windows.
Crop windows should be handled by considering them black outside the
crop region, not clamping.  This was leading to strange artifacts.

Also fix imagebuf.cpp getpixel/setpixel -- subtle difference between
Iterator::exists() [data exists for the pixel] versus valid() [pixel
coordinates is outside the iteration range].
Make ustring::TableRep match allocation & deallocation (malloc / free).
It was previously doing malloc / delete, a mismatch. Pointed out by Mark Leone.
Merge remote-tracking branch 'upstream/master'
Fix incorrectly named OpenEXR include files
oiiotool: work around iostream 'showpos' bug (used by tinyformat)
The bug that affected --croptofull with 0,0 origin.
It appears to be present only for some C++ library versions.  It's
been verified on a couple versions of OSX. Seems fine on Linux.
Fix build errors with alloca/isinf/isnan/isfinite, using MinGW on Windows.
Add a unit test for Timer.

Among other things, this unit test times how expensive a Timer is.
Answer: a Timer begin/end takes about 0.3 us on my OSX laptop, around
0.07 us on a souped-up Linux workstation.  YMMV on other platforms.  But
use this ballpark as guidance for the granularity of which things can
safely be timed without the Timer itself making things appreciably more
expensive.
Merge branch 'master' of https://github.com/OpenImageIO/oiio