gnu: icecat: Update to 38.6.0-gnu1.

* gnu/packages/patches/icecat-bug-1146335-pt1.patch,
  gnu/packages/patches/icecat-bug-1146335-pt2.patch,
  gnu/packages/patches/icecat-limit-max-buffers-size-for-ANGLE.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt01.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt02.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt03.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt04.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt05.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt06.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt07.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt08.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt09.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt10.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt11.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt12.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt13.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt14.patch,
  gnu/packages/patches/icecat-CVE-2016-1930-pt15.patch,
  gnu/packages/patches/icecat-CVE-2016-1935.patch: Delete files.
* gnu-system.am (dist_patch_DATA): Remove them.
* gnu/packages/gnuzilla.scm (icecat): Update to 38.6.0-gnu1.
  [source]: Remove patches.