expr: Fixup authors

* src/expr.c: Standardise the format of AUTHORS to
that used in other utils with multiple authors.
Also add Paul Eggert since he basically rewrote it
with his bignum fixes.
* AUTHORS (expr): Add Paul Eggert.

AUTHORS

@@ -25,7 +25,7 @@ du: Torbjörn Granlund, David MacKenzie, Paul Eggert, Jim Meyering
 echo: Brian Fox, Chet Ramey
 env: Richard Mlynarik, David MacKenzie
 expand: David MacKenzie
-expr: Mike Parker, James Youngman
+expr: Mike Parker, James Youngman, Paul Eggert
 factor: Paul Rubin
 false: Jim Meyering
 fmt: Ross Paterson

src/expr.c

@@ -145,7 +145,10 @@ mpz_out_str (FILE *stream, int base, mpz_t z)
 /* The official name of this program (e.g., no `g' prefix).  */
 #define PROGRAM_NAME "expr"
 
-#define AUTHORS proper_name ("Mike Parker"), proper_name ("James Youngman")
+#define AUTHORS \
+  proper_name ("Mike Parker"), \
+  proper_name ("James Youngman"), \
+  proper_name ("Paul Eggert")
 
 /* Exit statuses.  */
 enum