wscript: Fix internal waf error (missing features)

waf complains about missing features in the builder, so let's add some.

For the sake of completeness, here's an example error message:

Traceback (most recent call last):
  File "/home/adi/jack2/.waf-1.6.11-30618c54883417962c38f5d395f83584/waflib/Runner.py", line 162, in start
    st=tsk.runnable_status()
  File "/home/adi/jack2/.waf-1.6.11-30618c54883417962c38f5d395f83584/waflib/Task.py", line 285, in runnable_status
    new_sig=self.signature()
  File "/home/adi/jack2/.waf-1.6.11-30618c54883417962c38f5d395f83584/waflib/Task.py", line 274, in signature
    self.sig_implicit_deps()
  File "/home/adi/jack2/.waf-1.6.11-30618c54883417962c38f5d395f83584/waflib/Task.py", line 372, in sig_implicit_deps
    (nodes,names)=self.scan()
  File "/home/adi/jack2/.waf-1.6.11-30618c54883417962c38f5d395f83584/waflib/Tools/c_preproc.py", line 594, in scan
    raise Errors.WafError('%r is missing a feature such as "c", "cxx" or "includes": '%task.generator)
WafError: bld(uselib_local='clientlib', posted=True, features=[], idx=28, uselib='RT SNDFILE', meths=['process_rule', 'process_source'], prec=defaultdict(<type 'list'>, {}), includes=['../linux', '../posix', '../common/jack', '../common'], source=[/home/adi/jack2/example-clients/capture_client.c], mappings={}, path=/home/adi/jack2/example-clients, _name='jack_rec', target='jack_rec') in /home/adi/jack2/example-clients is missing a feature such as "c", "cxx" or "includes":

common/wscript

@@ -16,6 +16,7 @@ def configure(conf):
 
 def create_jack_process_obj(bld, target, sources, uselib = None):
     process = bld.new_task_gen('cxx', 'shlib')
+    process.features += 'cxx'
     process.env['shlib_PATTERN'] = '%s.so'
     process.defines  = ['HAVE_CONFIG_H','SERVER_SIDE']
     if bld.env['IS_MACOSX']:

example-clients/wscript

@@ -111,6 +111,7 @@ def build(bld):
 
     if bld.env['BUILD_EXAMPLE_CLIENT_REC']:
         prog = bld.new_task_gen('cc', 'program')
+        prog.features += 'cc'
         prog.includes = os_incdir + ['../common/jack', '../common']
         prog.source = 'capture_client.c'
         if bld.env['IS_MACOSX']:
@@ -127,6 +128,7 @@ def build(bld):
 
     if bld.env['IS_LINUX'] or bld.env['IS_MACOSX']:
         prog = bld.new_task_gen('cc', 'program')
+        prog.features += 'cc'
         prog.includes = os_incdir + ['../common/jack', '../common']
         prog.source = ['netsource.c', '../common/netjack_packet.c']
         prog.env.append_value("CCFLAGS", "-DNO_JACK_ERROR")
@@ -136,6 +138,7 @@ def build(bld):
 
     if bld.env['IS_LINUX'] and bld.env['BUILD_EXAMPLE_ALSA_IO']:
  	    prog = bld.new_task_gen('cc', 'program')
+	    prog.features += 'cc'
  	    prog.includes = os_incdir + ['../common/jack', '../common']
  	    prog.source = ['alsa_in.c', '../common/memops.c']
  	    prog.env.append_value("CCFLAGS", "-DNO_JACK_ERROR")
@@ -144,6 +147,7 @@ def build(bld):
  	    prog.target = 'alsa_in'
 
  	    prog = bld.new_task_gen('cc', 'program')
+	    prog.features += 'cc'
  	    prog.includes = os_incdir + ['../common/jack', '../common']
  	    prog.source = ['alsa_out.c', '../common/memops.c']
  	    prog.env.append_value("CCFLAGS", "-DNO_JACK_ERROR")
@@ -153,6 +157,7 @@ def build(bld):
 
     for example_lib, example_lib_source in list(example_libs.items()):
         lib = bld.new_task_gen('cc', 'shlib')
+        lib.features += 'cc'
         lib.env['shlib_PATTERN'] = '%s.so'
         lib.includes = os_incdir + ['../common/jack', '../common']
         lib.target = example_lib

linux/wscript

@@ -33,6 +33,7 @@ def create_jack_driver_obj(bld, target, sources, uselib = None):
 def build(bld):
     if bld.env['BUILD_JACKD'] == True:
         jackd = bld.new_task_gen('cxx', 'program')
+        jackd.features += 'cxx'
         jackd.includes = ['../linux', '../posix', '../common/jack', '../common', '../dbus']
         jackd.defines = ['HAVE_CONFIG_H','SERVER_SIDE']
         jackd.source = ['../common/Jackdmp.cpp']