Complete eqn.7 parsing. Features all productions from the original 1975

CACM paper in an LR(1) parse (1 -> eqn_rewind()).  Right now the code is
a little jungly, but will clear up as I consolidate parse components.
The AST structure will also be cleaned up, as right now it's pretty ad
hoc (this won't change the parse itself).  I added the mandoc_strndup()
function will here.

1 files changed, 6 insertions, 0 deletions

diff --git a/eqn.7 b/eqn.7
index 3f8b7f7c..b4910b2e 100644
--- a/eqn.7
+++ b/eqn.7
@@ -69,9 +69,14 @@ box     : text
         | UNDEF text
         | box pos box
         | box mark
+        | pile { list }
         | font box
         | SIZE text box
+        | LEFT text box [RIGHT text]
 text    : TEXT
+pile    : LPILE
+        | CPILE
+        | RPILE
 pos     : OVER
         | SUP
         | SUB
@@ -88,6 +93,7 @@ mark	: DOT
 font    : ROMAN
         | ITALIC
         | BOLD
+list    : eqn | list ABOVE eqn
 .Ed
 .Pp
 Data in TEXT form is a non-empty sequence of non-space characters or a