Let roff_getname() end the roff identifier at a tab character

and audit all its callers whether termination is handled correctly.

Resulting improvements:
* An escape or tab ending the macro name in a macro invocation
is discarded, and argument processing is started after it.
* An escape or tab ending a name in ".if d" and ".if r" is preserved.
* An escape ending a name in ".ds" causes the whole request to be ignored.
* A tab ending a name in ".ds" becomes part of the string.
* An escape or tab ending a name in ".rm"
causes the rest of the line to be ignored.
* An escape or tab ending the first name in ".als", ".rn", or ".nr"
causes the whole request to be ignored.

Kurt Jaeger <pi at FreeBSD> made me aware of
  https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=235456#c0
and in that bug report, comment 0 item (3) is a special case
of this class of issues.

Yes, the "mh" manual pages are no doubt among the worst on the planet.

1 files changed, 21 insertions, 0 deletions

diff --git a/regress/roff/de/tab.out_ascii b/regress/roff/de/tab.out_ascii
new file mode 100644
index 00000000..c2a82d87
--- /dev/null
+++ b/regress/roff/de/tab.out_ascii
@@ -0,0 +1,21 @@
+DE-TAB(1)                   General Commands Manual                  DE-TAB(1)
+
+NNAAMMEE
+     ddee--ttaabb - tab characters in macro definition lines
+
+DDEESSCCRRIIPPTTIIOONN
+     no argument: testval ;
+     argument after_tab: testval after_tab;
+     argument after_tab_and_space: testval after_tab_and_space;
+     argument after_two_tabs: testval   after_two_tabs;
+     argument after_tab_tab_space: testval   ;after_tab_tab_space
+
+   EEnndd mmaarrkkeerr
+     no argument: testval ;
+     argument after_tab: testval after_tab;
+
+   RReemmoovvaall
+     macro test1 is gone:
+     macro test2 still exists: testval ;
+
+OpenBSD                        February 6, 2019                        OpenBSD