Listed all the environment variables (MACHINE and PWD were missing).

Documented PWD.  MACHINE and MAKEOBJDIR are are still undocumented
except in main.c.  I will be changing MAKEOBJDIR back to its old
behaviour so that the comment in main.c actually applies.

Removed irrelevant misformatted text about make's name being argv[0].

usr.bin/make/make.1

@@ -388,8 +388,7 @@ sign.
 .It Ev MAKE
 The name that
 .Nm make
-was executed with
-.Pq Va argv Op 0
+was executed with.
 .It Va .CURDIR
 A path to the directory where
 .Nm make
@@ -411,6 +410,28 @@ variable which is then
 entered into the environment for all programs which
 .Nm make
 executes.
+.It Ev PWD
+Alternate path to the current directory.
+.Nm make
+normally sets 
+.Ql Va .CURDIR
+to the canonical path given by
+.Xr getcwd 2 .
+However, if the environment variable
+.Ql Ev PWD
+is set and gives a path to the current directory, then
+.Nm make
+sets
+.Ql Va .CURDIR
+to the value of
+.Ql Ev PWD
+instead.
+.Ql Ev PWD
+is set to the value of
+.Ql Va .OBJDIR
+for all programs which
+.Nm make
+executes.
 .El
 .Pp
 Variable expansion may be modified to select or modify each word of the
@@ -869,10 +890,12 @@ If no sources are specified, any previous specified suffices are deleted.
 .Sh ENVIRONMENT
 .Nm Make
 utilizes the following environment variables, if they exist:
+.Ev MACHINE ,
 .Ev MAKE ,
-.Ev MAKEFLAGS
+.Ev MAKEFLAGS ,
+.Ev MAKEOBJDIR ,
 and
-.Ev MAKEOBJDIR .
+.Ev PWD .
 .Sh FILES
 .Bl -tag -width /usr/share/mk -compact
 .It .depend