Issue 4991: Add installing optional URW++ fonts

Issue 4991: Add installing optional URW++ fonts

LilyPond default fonts (TeX Gyre) do not have Greek and Cyrillic glyphs.
Newest URW 35 fonts (June 2016) have them.
http://git.ghostscript.com/?p=urw-core35-fonts.git;a=commit;h=79bcdfb34fbce12b592cce389fa7a19da6b5b018

This commit realizes the followings.

. configure script finds the following 12 OTF files.
. If they are found, `make install` installs them.
  (Both TeX Gyre and URW fons are installed
   under the lilypond fonts directory.)
. Even if they are not found, configure script does not raise error.
  (Only TeX Gyre fonts are installed.)

C059-BdIta.otf
C059-Bold.otf
C059-Italic.otf
C059-Roman.otf

NimbusMonoPS-Bold.otf
NimbusMonoPS-BoldItalic.otf
NimbusMonoPS-Italic.otf
NimbusMonoPS-Regular.otf

NimbusSans-Bold.otf
NimbusSans-BoldOblique.otf
NimbusSans-Oblique.otf
NimbusSans-Regular.otf