make sure all mp functions are accounted for

Reference: /n/sources/patch/maybe/mpmannit
Date: Sun Dec  2 02:57:15 CET 2012
Signed-off-by: quanstro@quanstro.net

--- /sys/man/2/mp	Sun Dec  2 02:57:08 2012
+++ /sys/man/2/mp	Sun Dec  2 02:57:05 2012
@@ -1,6 +1,6 @@
 .TH MP 2
 .SH NAME
-mpsetminbits, mpnew, mpfree, mpbits, mpnorm, mpcopy, mpassign, mprand, strtomp, mpfmt,mptoa, betomp, mptobe, letomp, mptole, mptoui, uitomp, mptoi, itomp, uvtomp, mptouv, vtomp, mptov, mpdigdiv, mpadd, mpsub, mpleft, mpright, mpmul, mpexp, mpmod, mpdiv, mpcmp, mpextendedgcd, mpinvert, mpsignif, mplowbits0, mpvecdigmuladd, mpvecdigmulsub, mpvecadd, mpvecsub, mpveccmp, mpvecmul, mpmagcmp, mpmagadd, mpmagsub, crtpre, crtin, crtout, crtprefree, crtresfree \- extended precision arithmetic
+mpsetminbits, mpnew, mpfree, mpbits, mpnorm, mpcopy, mpassign, mprand, strtomp, mpfmt,mptoa, betomp, mptobe, letomp, mptole, mptoui, uitomp, mptoi, itomp, uvtomp, mptouv, vtomp, mptov, mpdigdiv, mpadd, mpsub, mpleft, mpright, mpmul, mpexp, mpmod, mpdiv, mpfactorial, mpcmp, mpextendedgcd, mpinvert, mpsignif, mplowbits0, mpvecdigmuladd, mpvecdigmulsub, mpvecadd, mpvecsub, mpveccmp, mpvecmul, mpmagcmp, mpmagadd, mpmagsub, crtpre, crtin, crtout, crtprefree, crtresfree \- extended precision arithmetic
 .SH SYNOPSIS
 .B #include <u.h>
 .br
@@ -112,6 +112,9 @@
 	mpint *remainder)
 .PP
 .B
+mpint*	mpfactorial(ulong n)
+.PP
+.B
 int	mpcmp(mpint *b1, mpint *b2)
 .PP
 .B
@@ -465,6 +468,9 @@
 .BR "quotient = dividend/divisor" .
 .BR "remainder = dividend % divisor" .
 .TP
+.I mpfactorial
+Return a newly allocated
+.BR "fact = n!" .
 .I mpcmp
 returns -1, 0, or +1 as
 .I b1