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, 41 insertions, 0 deletions

diff --git a/regress/roff/de/tab.in b/regress/roff/de/tab.in
new file mode 100644
index 00000000..5f85fe21
--- /dev/null
+++ b/regress/roff/de/tab.in
@@ -0,0 +1,41 @@
+.\" $OpenBSD: tab.in,v 1.1 2019/02/06 20:54:28 schwarze Exp $
+.Dd $Mdocdate: February 6 2019 $
+.Dt DE-TAB 1
+.Os
+.Sh NAME
+.Nm de-tab
+.Nd tab characters in macro definition lines
+.Sh DESCRIPTION
+.de test1	ignored
+testval \\$1;\\$2
+..
+no argument:
+.test1
+.br
+argument after_tab:
+.test1	after_tab
+.br
+argument after_tab_and_space:
+.test1	 after_tab_and_space
+.br
+argument after_two_tabs:
+.test1		after_two_tabs
+.br
+argument after_tab_tab_space:
+.test1		 after_tab_tab_space
+.Ss End marker
+.de test2 endm	ignored
+testval \\$1;\\$2
+.endm
+no argument:
+.test2
+.br
+argument after_tab:
+.test2	after_tab
+.Ss Removal
+.rm test1	test2
+macro test1 is gone:
+.test1
+.br
+macro test2 still exists:
+.test2