Correct the description of the MFLAGS and .MAKEFLAGS variables. Add

the MFLAGS target. Document that variable assignments from the MAKEFLAGS
environment variable and the .MAKEFLAGS and .MFLAGS target have the
same precedence as command line variable assignments.

usr.bin/make/make.1

@@ -395,7 +395,12 @@ environment.
 .It Global variables
 Variables defined in the makefile or in included makefiles.
 .It Command line variables
-Variables defined as part of the command line.
+Variables defined as part of the command line and variables
+obtained from the
+.Ev MAKEFLAGS
+environment variable or the
+.Ic .MAKEFLAGS
+target.
 .It Local variables
 Variables that are defined specific to a certain target.
 The seven local variables are as follows:
@@ -559,9 +564,9 @@ Its contents are stored in
 .Nm Ns 's
 .Va .MAKEFLAGS
 variable.
-Anything specified on
+All options and variable assignment specified on
 .Nm Ns 's
-command line is appended to the
+command line are appended to the
 .Va .MAKEFLAGS
 variable which is then
 entered into the environment as
@@ -570,9 +575,12 @@ for all programs which
 .Nm
 executes.
 .It Va MFLAGS
-A synonym for
-.Va .MAKEFLAGS
-provided for backward compatibility.
+is provided for backward compatibility and
+contains all the options from the
+.Ev MAKEFLAGS
+environment variable plus any options specified on
+.Nm Ns 's
+command line.
 .It Va .TARGETS
 List of targets
 .Nm
@@ -1131,6 +1139,8 @@ The flags are as if typed to the shell, though the
 .Fl f
 option will have
 no effect.
+.It Ic .MFLAGS
+Same as above, for backward compatibility.
 .\" XXX: NOT YET!!!!
 .\" .It Ic .NOTPARALLEL
 .\" The named targets are executed in non parallel mode. If no targets are