Log Message:
leptonica: updated to 1.75.0

This is a new version, for major Ubuntu release 18.04.
$TMPDIR path rewriting turned off on Unix; only used for Windows.
Added pix conversion to depth 2 and 4.  We now have general
  converters to 1, 2, 4, 8, 16 and 32 bpp.
Modified giflib to use read/write from/to memory; no temp files;
  no longer support versions before 5.1.
Move most low-level code from separate files to their callers;
  about 30 of them became static.
Improved table detection on scanned page images (tests: pageseg_reg.c)
Added support for write/compare regression tests for files.
Modified printimage for more flexibility.
Enable lookup by key on comma-separated key/value text file.
Update README.html for building with Visual Studio.
Improved functions for getting pixel averages in RGB images
Simplified and speedup of unsharp masking.
New function for detecting and correcting text orientation.
Remove slow sharpening operation when not appropriate during scaling.
Better handling of gplots with 0 or 1 data point.
Coverity scan fixes.
Modified jpeg2000 header to use openjpeg 2.3.
Improved depth accessors for pixa and pixaa; added size accessors
  for pixa and pixaa.
Bug fix in webp interface on read error.
New function that finds the closest boxes in a boxa to any particular
  box, in each of 4 directions.
New regression tests in automated sequence: blend5_reg, quadtree_reg,
wordboxes_reg.
New program: textorient
Removed programs: snapcolortest