docs/machine*: Remove explicit targets and "machine." prefixes on classes.

With currentmodule:: set properly, none are needed. Extra "machine." prefix
produces wrong indexing data.

docs/library/machine.ADC.rst

 .. currentmodule:: machine
-.. _machine.ADC:
 
 class ADC -- analog to digital conversion
 =========================================
@@ -15,7 +14,7 @@ Usage::
 Constructors
 ------------
 
-.. class:: machine.ADC(id=0, \*, bits=12)
+.. class:: ADC(id=0, \*, bits=12)
 
    Create an ADC object associated with the given pin.
    This allows you to then read analog values on that pin.

docs/library/machine.I2C.rst

 .. currentmodule:: machine
-.. _machine.I2C:
 
 class I2C -- a two-wire serial protocol
 =======================================
@@ -45,14 +44,14 @@ Constructors
 
 .. only:: port_wipy
 
-    .. class:: machine.I2C(bus, ...)
+    .. class:: I2C(bus, ...)
 
        Construct an I2C object on the given bus.  `bus` can only be 0.
        If the bus is not given, the default one will be selected (0).
 
 .. only:: port_esp8266
 
-    .. class:: machine.I2C(scl, sda, \*, freq=400000)
+    .. class:: I2C(scl, sda, \*, freq=400000)
 
        Construct and return a new I2C object.
        See the init method below for a description of the arguments.

docs/library/machine.Pin.rst

@@ -58,7 +58,7 @@ Usage Model:
 Constructors
 ------------
 
-.. class:: machine.Pin(id, ...)
+.. class:: Pin(id, ...)
 
    Create a new Pin object associated with the id.  If additional arguments are given,
    they are used to initialise the pin.  See :meth:`Pin.init`.

docs/library/machine.RTC.rst

 .. currentmodule:: machine
-.. _machine.RTC:
 
 class RTC -- real time clock
 ============================
@@ -17,7 +16,7 @@ Example usage::
 Constructors
 ------------
 
-.. class:: machine.RTC(id=0, ...)
+.. class:: RTC(id=0, ...)
 
    Create an RTC object. See init for parameters of initialization.
 

docs/library/machine.SD.rst

 .. currentmodule:: machine
-.. _machine.SD:
 
 class SD -- secure digital memory card
 ======================================
@@ -25,7 +24,7 @@ Example usage::
 Constructors
 ------------
 
-.. class:: machine.SD(id,... )
+.. class:: SD(id,... )
 
    Create a SD card object. See ``init()`` for parameters if initialization. 
 

docs/library/machine.SPI.rst

 .. currentmodule:: machine
-.. _machine.SPI:
 
 class SPI -- a master-driven serial protocol
 ============================================
@@ -24,7 +23,7 @@ Constructors
 
 .. only:: port_wipy
 
-    .. class:: machine.SPI(id, ...)
+    .. class:: SPI(id, ...)
 
        Construct an SPI object on the given bus.  ``id`` can be only 0.
        With no additional parameters, the SPI object is created but not

docs/library/machine.Timer.rst

 .. currentmodule:: machine
-.. _machine.Timer:
 
 class Timer -- control internal timers
 ======================================
@@ -60,7 +59,7 @@ class Timer -- control internal timers
 Constructors
 ------------
 
-.. class:: machine.Timer(id, ...)
+.. class:: Timer(id, ...)
 
     .. only:: port_wipy
 

docs/library/machine.UART.rst

 .. currentmodule:: machine
-.. _machine.UART:
 
 class UART -- duplex serial communication bus
 =============================================
@@ -59,7 +58,7 @@ Constructors
 
 .. only:: port_wipy
 
-    .. class:: machine.UART(bus, ...)
+    .. class:: UART(bus, ...)
     
        Construct a UART object on the given bus.  ``bus`` can be 0 or 1.
        If the bus is not given, the default one will be selected (0) or the selection

docs/library/machine.WDT.rst

 .. currentmodule:: machine
-.. _machine.WDT:
 
 class WDT -- watchdog timer
 ===========================
@@ -18,7 +17,7 @@ Example usage::
 Constructors
 ------------
 
-.. class:: machine.WDT(id=0, timeout=5000)
+.. class:: WDT(id=0, timeout=5000)
 
    Create a WDT object and start it. The timeout must be given in seconds and
    the minimum value that is accepted is 1 second. Once it is running the timeout