add Makefile.config, change all Makefile includes

Moved makefile variables that configure calc and configure how to
compile calc from Makefile into a new Makefile.config file.

The Makeifle includes the Makefile.config file.
The cal/Makeifle includes the Makefile.config file.
The cscript/Makeifle includes the Makefile.config file.
The custom/Makeifle includes the Makefile.config file.
The help/Makeifle includes the Makefile.config file.

Now, the Makefile.config file will consistently configure
calc and how calc is compiled and built by all calc Makefiles.

The platform target section from the old Makefile has been moved to
a new file, Makefile.target.  The custom/Makefile no longer includes
Makefile.

The Makeifle includes the Makefile.target file.
The cal/Makeifle includes the Makefile.target file.
The cscript/Makeifle includes the Makefile.target file.
The custom/Makeifle includes the Makefile.target file.
The help/Makeifle includes the Makefile.target file.

Now, the Makefile.target file will consistently set
target information for all calc Makefiles.

The cal/Makeifle includes the Makefile.local file.
The cscript/Makeifle includes the Makefile.local file.
The custom/Makeifle includes the Makefile.local file.
The help/Makeifle includes the Makefile.local file.

Thus, one may modify or append many Makefile variables
in all calc Makefiles.

HOWTO.INSTALL

@@ -9,6 +9,7 @@ and see if there is a pre-compiled version of calc that you may install.
 Open up the 'Assets' tag below a given release and download these RPMs:
 
     * calc*.rpm
+
 	- all that is needed if you just want to use calc
 
 If your platform supports rpm and matches one of the "calc*.rpm" files, you
@@ -23,6 +24,7 @@ In addition, if your platform supports rpm and matches one of the
 files for use in other programs:
 
     * calc-devel-*.rpm
+
 	- calc *.h header and *.a lib files for use in other programs
 
 Alternately to the above github link, you might try looking at the RPMs under:
@@ -81,9 +83,6 @@ than the top of the master branch.
 
 ## Step 1: Makefile considerations
 
-Look at Makefile, and adjust it to suit your needs.
-
-
 
 ### IMPORTANT: Make support of conditional syntax required:
 
@@ -100,21 +99,48 @@ The Gnu Make is not required per-se, just a modern make tool
 that supports "Conditional syntax".
 
 
+### Review Makefiles
 
-### Suggestion: Modify Makefile.local instead of Makefile:
+Review Makefile.config and Makefile.target.
+
+If you are curious, review Makefile as well, although
+there may be little in the main Makefile that you may
+want to change.
+
+Consider modifying Makefile.local by replace values or
+appending values found in Makefile.config and Makefile.target.
+
+If you are adding custom functions, review custom/Makefile
+and modify custom/Makefile as needed.
+
+
+
+### Suggestion: Modify Makefile.local
+
+All Makefiles include Makefile.local just before the
+first and default all rule.  So Makefile.local may be
+used to modify, replace or append values to Makefile variables.
 
 In most cases, to change the way that calc is made, consider
-adding lines to Makefile.local instead of modifying Makefile.
+adding lines to Makefile.local instead of modifying other Makefiles.
 
-A recommened way to adjust it is to add lines to: Makefile.local
+A recommended way to adjust it is to add lines to: Makefile.local
 using the := syntax to replace values such as:
 
     DEBUG:= -O0 -g
 
 or by using the += syntax to append to values such as:
 
-    CFLAGS+= -UCUSTOM
+    DEBUG+= -ipa
 
+You can, of course, modify other Makefiles.  We only
+suggest using Makefile.local to minimize the number
+of source files you modify.
+
+And finally, you can always just add arguments to your
+make command line instead of modifying a Makefile.  For example:
+
+    make clobber all DEBUG="-O0 -g"
 
 
 ## readline package assumed by default:
@@ -167,6 +193,8 @@ or add to Makefile.local, these lines:
     READLINE_INCLUDE=
     READLINE_LIB=
 
+See the "Suggestion: Modify Makefile.local" section above for
+information on the Makefile.local file.
 
 
 ### Windows or a Windows-like environments:
@@ -230,6 +258,8 @@ instead of Makefile" above.  For example:
 
     T:= /var/tmp/testing
 
+See the "Suggestion: Modify Makefile.local" section above for
+information on the Makefile.local file.
 
 
 ### platform target section
@@ -286,11 +316,11 @@ See the BUGS file if you find any compiler warning or errors.
 
 You may run the calc regression test suite, after successfully compiling, by:
 
-	make check
+    make check
 
 For a more quiet check which only prints if something goes wrong, use:
 
-	make chk
+    make chk