Update fonts/Hack-ttf to Hack-ttf-2.015.

pkgsrc changes (no functional changes intended):
 o unset USE_LANGUAGES
 o use NO_BUILD instead of defining an empty do-build target

Changes:
# Version 2.015 (release build)
Changes vs. release v2.013:
- new vertical metrics = decreased line spacing height - Issues #28, #32, #39,
  #41, #95, #103
- adjusted vertical position of the colon to a higher position, improves
  alignment with other punctuation glyphs (U+003A) - Issue #66
- changed vertical position of the dash (U+002D) so that regular and oblique,
  bold and bold oblique are properly aligned - Issue #107
- updated hinting algorithm for bold set (improved point position over stem of
  lowercase j/i for some text sizes) - Issue #84
- underscore (U+005F) centered, increased width, increased height & aligned
  vertical position closer to baseline - Issues #97, #98, #100, 103,
- increased vertical position of dieresis mark on lowercase u dieresis
  (U+00FC) - Issue #61
- increased vertical position of dieresis mark on lowercase i dieresis (U+00EF)
- increased vertical position of dieresis mark on lowercase e dieresis (U+00EB)
- decreased vertical position of the asterisk (U+002A) - Issue #34
- new design for ascii tilde - broader curves, taller glyph with goal to
  improve appearance at small text sizes where it tended to render like a dash
  (U+007E) - Issue #37
- new ttf build autohinting script
  (./postbuild_processing/tt-hinting/autohint.sh)
- new ttf build autohinting Control Instructions File - bold set
  (./postbuild_processing/tt-hinting/Hack-Bold-TA.txt)
- new ttf build release script (./postbuild_processing/tt-hinting/release.sh)
- new web font release script
  (./postbuild_processing/webfonts/releasewebfonts.sh)
- new vfb to UFO source file conversion script (./tools/makeufo.sh)
- new UFO source file types - includes separate source files for TrueType
  (`*-TT.ufo`) and PostScript (`*-PS.ufo`) releases
- source file path changes: now includes separate `ufo` and `vfb` directories
  under the `./source` repository directory
- Hack Open Font license updated to version 2.0.  The license changes better
  define the Hack project as a derivative project of the Bitstream Vera Sans
  Mono typeface project and are intended to make the license more consistent
  with the Bitstream Vera libre, open source license under which Hack is
  co-licensed.  There are no new restrictions on use of the fonts with these
  license changes.  Embedding permissions are made explicit in this version
  of the Hack Open Font license.

# Version 2.013 (release build)
Changes vs. release v2.010:
- Fixed missing middle dot glyph (U+00B7), adjusted width of U+00B7 em box to
  address spacing issues in editors that highlight empty spaces
  (Issues #27 & #46)
- Powerline glyph alignment and size adjustments (Issue #33)
- Fixed name tables to address:
  - incorrect oblique rendering with Java type renderers on OS X (Issue #26)
  - incorrect italic + bold + bold oblique rendering in some syntax
    highlighters (Issues #42, #50, #60)
  - backslash character took inappropriate vertical alignment because of
    incorrect slant angle in some editors (Issue #67)
- Changed oblique and bold oblique font names to "Hack Italic" and "Hack Bold
  Italic" to address Windows listings
- Changed oblique and bold oblique webfont names to "hack-italic-webfont.[xxx]"
  and "hack-bolditalic-webfont.[xxx]"
- Changed oblique and bold oblique basic Latin + Latin-1 webfont subsets to the
  names "hack-italic-latin-webfont.[xxx]" and
  "hack-bolditalic-latin-webfont.[xxx]"
- Changed license name from "Modified SIL Open Font License" to "Hack Open Font
  License" to comply with SIL regulations for SIL Open Font License
  modifications
- Removed all license references to SIL to comply with SIL regulations for
  modifications of the SIL Open Font License
- Removed SIL Open Font License preamble from the Hack Open Font License to
  comply with SIL regulations for modifications of the SIL Open Font License
- Removed the following statement from Hack Open Font License condition #3:
  "This restriction only applies to the primary font name as presented to the
  users." to address a reserved font name conflict with the Bitstream Vera
  license
- Modified the build directory structure for the Hack web fonts
- Added Hack webfont CSS files to the build directory


(leot)