Import mdocml 1.12.3 from upstream CVS as of today.

Changes in version 1.12.3, released on December 31, 2013

 * In the mdoc(7) SYNOPSIS, line breaks and hanging indentation
   now work correctly for .Fo/.Fa/.Fc and .Fn blocks.
   Thanks to Franco Fichtner for doing part of the work.
 * The mdoc(7) .Bk macro got some addititonal bugfixes.
 * In mdoc(7) macro arguments, double quotes can now be quoted
   by doubling them, just like in man(7).
   Thanks to Tsugutomo ENAMI for the patch.
 * At the end of man(7) macro lines, end-of-sentence spacing
   now works.  Thanks to Franco Fichtner for the patch.
 * For backward compatibility, the man(7) parser now supports the
   man-ext .UR/.UE (uniform resource identifier) block macros.
 * The man(7) parser now handles closing blocks that are not open
   more gracefully.
 * The man(7) parser now ignores blank lines right after .SH and .SS.
 * In the man(7) formatter, reset indentation when leaving a block,
   not just when entering the next one.
 * The roff(7) .nr request now supports incrementing and decrementing
   number registers and stops parsing the number right before the
   first non-digit character.
 * The roff(7) parser now supports the alternative escape sequence
   syntax \C'uXXXX' for Unicode characters.
 * The roff(7) parser now parses and ignores the .fam (font family)
   and .hw (hyphenation points) requests and the \d and \u escape
   sequences.
 * The roff(7) manual got a new ESCAPE SEQUENCE REFERENCE.

Changes in version 1.12.2, released on Oktober 5, 2013

 * The mdoc(7) to man(7) converter, to be called as mandoc -Tman,
   is now fully functional.
 * The mandoc(1) utility now supports the -Ios (default operating system)
   input option, and the -Tutf8 output mode now actually works.
 * The mandocdb(8) utility no longer truncates existing databases when
   starting to build new ones, but only replaces them when the build
   actually succeeds.
 * The man(7) parser now supports the PD macro (paragraph distance),
   and (for GNU man-ext compatibility only) EX (example block) and EE
   (example end).  Plus several bugfixes regarding indentation, line
   breaks, and vertical spacing, and regarding RS following TP.
 * The roff(7) parser now supports the \f(BI (bold+italic) font escape,
   the \z (zero cursor advance) escape and the cc (change control
   character) and it (input line trap) requests. Plus bugfixes regarding
   the \t (tab) escape, nested escape sequences, and conditional requests.
 * In mdoc(7), several bugs were fixed related to UTF-8 output of quoting
   enclosures, delimiter handling, list indentation and horizontal and
   vertical spacing, formatting of the Lk, %U, and %C macros, plus some
   bugfixes related to the handling of syntax errors like badly nested
   font blocks, stray Ta macros outside column lists, unterminated It Xo
   blocks, and non-text children of Nm blocks.
 * In tbl(7), the width of horizontal spans and the vertical spacing
   around tables was corrected, and in man(7) files, a crash was fixed
   that was triggered by some particular unclosed T{ macros.
 * For mandoc developers, we now provide a tbl(3) library manual and
   gmdiff, a very small, very simplistic groff-versus-mandoc output
   comparison tool.