patch #7688: Implement parent programmers feature

* avrdude.conf.in: updated documentation comment and some programmers 
    have now parents
  * config_gram.y: initpgm will now called at first use of programmer 
    in main. parser sets only the function pointer in the pgm structure.
    Pin and pin lists definitions can now be empty to remove the parents
    setting.
  * doc/avrdude.texi: updated documentation
  * main.c: added call to pgm->initpgm after locate_programmer
  * pgm.[hc]: added field initpgm in structure, added function pgm_dup


git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk/avrdude@1045 81a1dc3b-b13d-400b-aceb-764788c761c2

doc/avrdude.texi

@@ -1432,6 +1432,7 @@ The format of the programmer definition is as follows:
 
 @smallexample
 programmer
+    parent <id>                                 # <id> is a quoted string
     id       = <id1> [, <id2> [, <id3>] ...] ;  # <idN> are quoted strings
     desc     = <description> ;                  # quoted string
     type     = par | stk500 | ... ;             # programmer type (see below for a list)
@@ -1455,6 +1456,10 @@ programmer
   ;
 @end smallexample
 
+@noindent
+If a parent is specified, all settings of it (except its ids) are used for the new 
+programmer. These values can be changed by new setting them for the new programmer.
+
 @noindent
 To invert a bit in the pin definitions, use @code{= ~ <num>}.