COMP: Fix compiler warnings with ITK_USE_SYSTEM_VXL

Commit 41793b40 attempted to solve an unused variable warning by forking
VXL. The warning was still triggered when ITK_USE_SYSTEM_VXL was enabled.

This reverts the fork of VXL and solves the warning when using system VXL
too.

Change-Id: I61db91d3269818a4819541dc5ec6a25d273f3dd2
ENH: Add SetJPEGQuality method

Adds Set/GetJPEGQuality to expose control of the compression quality of
the JPEG compression.

Adds three regression tests for quality settings: 1, 50, 100.

Change-Id: Ia47a86ce0c2bc2f042cf0973713b2dbc81d1ec9f
Merge topic 'VNL-Diag-Warning'

0cfabd0 COMP: Fix compiler warnings with ITK_USE_SYSTEM_VXL
Merge topic 'TIFFImageIO_JPEGQuality'

c8c3e21 ENH: Add SetJPEGQuality method