fix testcases to silent GCC warning

tests/errors/compile_time_unraisable_T370.pyx

 
 cdef int raiseit():
     raise IndexError
+if False: raiseit()
 
 _ERRORS = u"""
 FIXME: provide a good error message here.

tests/run/autotestdict.pyx

@@ -30,6 +30,7 @@ cdef cdeffunc():
     >>> True
     False
     """
+cdeffunc()
 
 def all_tests_run():
     log.sort()

tests/run/bufaccess.pyx

@@ -53,6 +53,8 @@ def printbuf():
     """
     cdef object[int, ndim=2] buf
     print buf
+    return
+    buf[0,0] = 0
 
 @testcase
 def acquire_release(o1, o2):

tests/run/for_decrement.pyx

@@ -19,7 +19,7 @@ def range_loop_indices():
     Optimized integer for loops using range() should follow Python behavior, 
     and leave the index variable with the last value of the range.
     """
-    cdef int i, j, k=0, l, m
+    cdef int i, j, k=0, l=10, m=10
     for i in range(10): pass
     for j in range(2,10): pass
     for k in range(0,10,get_step()): pass