Fix ReST markup wrt. literal code blocks.

pep-3112.txt

@@ -23,22 +23,22 @@ spell ASCII strings and arbitrary binary data.
 Motivation
 ==========
 
-Existing spellings of an ASCII string in Python 3000 include:
+Existing spellings of an ASCII string in Python 3000 include::
 
     bytes('Hello world', 'ascii')
     'Hello world'.encode('ascii')
 
-The proposed syntax is:
+The proposed syntax is::
 
     b'Hello world'
 
-Existing spellings of an 8-bit binary sequence in Python 3000 include:
+Existing spellings of an 8-bit binary sequence in Python 3000 include::
 
     bytes([0x7f, 0x45, 0x4c, 0x46, 0x01, 0x01, 0x01, 0x00])
     bytes('\x7fELF\x01\x01\x01\0', 'latin-1')
     '7f454c4601010100'.decode('hex')
 
-The proposed syntax is:
+The proposed syntax is::
 
     b'\x7f\x45\x4c\x46\x01\x01\x01\x00'
     b'\x7fELF\x01\x01\x01\0'
@@ -46,12 +46,12 @@ The proposed syntax is:
 In both cases, the advantages of the new syntax are brevity, some
 small efficiency gain, and the detection of encoding errors at compile
 time rather than at runtime.  The brevity benefit is especially felt
-when using the string-like methods of bytes objects:
+when using the string-like methods of bytes objects::
 
     lines = bdata.split(bytes('\n', 'ascii'))  # existing syntax
     lines = bdata.split(b'\n')  # proposed syntax
 
-And when converting code from Python 2.x to Python 3000:
+And when converting code from Python 2.x to Python 3000::
 
     sok.send('EXIT\r\n')  # Python 2.x
     sok.send('EXIT\r\n'.encode('ascii'))  # Python 3000 existing