all: Prune trailing whitespace.

Prune trailing whitespace across the whole project (almost), done
automatically with:

    grep -IUrl --color "[[:blank:]]$" --exclude-dir=.git --exclude=*.exp |\
        xargs sed -i 's/[[:space:]]*$//'

Exceptions:
- Skip third-party code in lib/ and drivers/cc3100/
- Skip generated code in bluetooth_init_cc2564C_1.5.c
- Preserve command output whitespace in docs, eg:
  docs/esp8266/tutorial/repl.rst

Signed-off-by: Phil Howard <phil@gadgetoid.com>

docs/library/machine.ADCBlock.rst

@@ -26,7 +26,7 @@ Constructors
 
    Access the ADC peripheral identified by *id*, which may be an integer
    or string.
-   
+
    The *bits* argument, if given, sets the resolution in bits of the
    conversion process.  If not specified then the previous or default
    resolution is used.

docs/library/machine.PWM.rst

@@ -86,7 +86,7 @@ Specific PWM class implementations
 
 The following concrete class(es) implement enhancements to the PWM class.
 
-   | :ref:`pyb.Timer for PyBoard <pyb.Timer>`  
+   | :ref:`pyb.Timer for PyBoard <pyb.Timer>`
 
 Limitations of PWM
 ------------------
@@ -103,7 +103,7 @@ Limitations of PWM
   Some ports like the RP2040 one use a fractional divider, which allow a finer
   granularity of the frequency at higher frequencies by switching the PWM
   pulse duration between two adjacent values, such that the resulting average
-  frequency is more close to the intended one, at the cost of spectral purity. 
+  frequency is more close to the intended one, at the cost of spectral purity.
 
 * The duty cycle has the same discrete nature and its absolute accuracy is not
   achievable.  On most hardware platforms the duty will be applied at the next