waf: ardupilotwaf: allow multiple program groups for program

The program_dir defaults to the first group's name. That feature will be useful
for "copter" build command, which will build all frame types.

Tools/CPUInfo/wscript

@@ -4,5 +4,5 @@
 def build(bld):
     bld.ap_program(
         use='ap',
-        program_group='tools',
+        program_groups='tools',
     )

Tools/Replay/wscript

@@ -10,5 +10,5 @@ def build(bld):
 
     bld.ap_program(
         use='ap',
-        program_group='tools',
+        program_groups='tools',
     )

Tools/ardupilotwaf/ardupilotwaf.py

@@ -86,7 +86,7 @@ _grouped_programs = {}
 
 @conf
 def ap_program(bld,
-               program_group='bin',
+               program_groups='bin',
                program_dir=None,
                use_legacy_defines=True,
                program_name=None,
@@ -106,8 +106,10 @@ def ap_program(bld,
 
     kw['features'] = kw.get('features', []) + bld.env.AP_PROGRAM_FEATURES
 
+    program_groups = Utils.to_list(program_groups)
+
     if not program_dir:
-        program_dir = program_group
+        program_dir = program_groups[0]
 
     name = os.path.join(program_dir, program_name)
 
@@ -126,11 +128,13 @@ def ap_program(bld,
         program_dir=program_dir,
         **kw
     )
-    _grouped_programs.setdefault(program_group, []).append(tg)
+
+    for group in program_groups:
+        _grouped_programs.setdefault(group, []).append(tg)
 
 @conf
 def ap_example(bld, **kw):
-    kw['program_group'] = 'examples'
+    kw['program_groups'] = 'examples'
     ap_program(bld, **kw)
 
 # NOTE: Code in libraries/ is compiled multiple times. So ensure each
@@ -193,7 +197,7 @@ def ap_find_tests(bld, use=[]):
             source=[f],
             use=use,
             program_name=f.change_ext('').name,
-            program_group='tests',
+            program_groups='tests',
             use_legacy_defines=False,
             cxxflags=['-Wno-undef'],
         )
@@ -213,7 +217,7 @@ def ap_find_benchmarks(bld, use=[]):
             source=[f],
             use=use,
             program_name=f.change_ext('').name,
-            program_group='benchmarks',
+            program_groups='benchmarks',
             use_legacy_defines=False,
         )