Merge branch 'refs/heads/t/base64'

A couple of patches which move the base64 code to a separate file,
and improve on it. Was cooking for several months.

* refs/heads/t/base64:
  base64: Speed up decoder by using a table.
  base64: Use para_isspace() everywhere.
  base64: Trivial whitespace fixes.
  base64: Replace Pad64 variable by macro.
  base64: Remove unnecessary overflow checks.
  base64: Saner semantics for base64_decode() and uudecode().
  Move base64 implementation to own file.

diff --cc NEWS.md
index afc7f1054d9df40371a6594255c6e47b4baf356b,71eb6cb26d3a333f8840f78848ad74986f689754..b0862d5f392ee33504255eab1d0d43e3ee157067
--- 1/NEWS.md
--- 2/NEWS.md
+++ b/NEWS.md
@@@ -1,16 -1,6 +1,16 @@@
  NEWS
  ====
  
- 
 +------------------------------------------
 +0.5.7 (to be announced) "semantic density"
 +------------------------------------------
++- Speedup of the base64 decoder.
 +- One of the two source browsers has been removed from the web pages.
 +  The doxygen API reference still contains an HTML version of each
 +  source file.
 +
 +Download: [tarball](./releases/paraslash-git.tar.bz2)
 +
  ---------------------------------------
  0.5.6 (2016-07-10) "cascading gradient"
  ---------------------------------------

diff --cc error.h
Simple merge