Use string literals for namespace (rather than dotted names).

Cython/Compiler/Parsing.py

@@ -2278,7 +2278,7 @@ def p_cdef_extern_block(s, pos, ctx):
         _, include_file = p_string_literal(s)
     if s.systring == "namespace":
         s.next()
-        ctx.namespace = p_dotted_name(s, as_allowed=False)[2].replace('.', '::')
+        ctx.namespace = p_string_literal(s)[1]
     ctx = ctx(cdef_flag = 1, visibility = 'extern')
     if p_nogil(s):
         ctx.nogil = 1

tests/run/cpp_classes.pyx

@@ -7,7 +7,7 @@ __doc__ = u"""
     (225.0, 225.0)
 """
 
-cdef extern from "shapes.h" namespace shapes:
+cdef extern from "shapes.h" namespace "shapes":
 
     cdef cppclass Shape:
         float area()

tests/run/cpp_stl.pyx

@@ -5,7 +5,7 @@ __doc__ = u"""
     100
 """
 
-cdef extern from "vector" namespace std:
+cdef extern from "vector" namespace "std":
 
     cdef cppclass iterator[T]:
         pass

tests/run/cpp_stl_vector.pyx

-cdef extern from "<vector>" namespace std:
+cdef extern from "<vector>" namespace "std":
 
     cdef cppclass vector[T]:
         void push_back(T)