Typos in pin parameter descriptions (#88)

* Typos in pin parameter descriptions

* 'name of pin'

libs/core/pins.cpp

@@ -134,7 +134,7 @@ namespace pins {
 
     /**
      * Read the connector value as analog, that is, as a value comprised between 0 and 1023.
-     * @param name pin to write to, eg: AnalogPin.P1
+     * @param name of pin to read from, eg: AnalogPin.P1
      */
     //% help=pins/analog-read-pin weight=25
     //% blockId=device_get_analog_pin block="analog read|pin %name" blockGap="8"
@@ -146,7 +146,7 @@ namespace pins {
 
     /**
      * Set the connector value as analog. Value must be comprised between 0 and 1023.
-     * @param name pin name to write to, eg: AnalogPin.P1
+     * @param name of pin to write to, eg: AnalogPin.P1
      * @param value value to write to the pin between ``0`` and ``1023``. eg:1023,0
      */
     //% help=pins/analog-write-pin weight=24
@@ -296,7 +296,7 @@ namespace pins {
     }
 
     /**
-     * Emit a plse-width modulation (PWM) signal to the current pitch pin. Use `analog set pitch pin` to define the pitch pin.
+     * Emit a pulse-width modulation (PWM) signal to the current pitch pin. Use `analog set pitch pin` to define the pitch pin.
      * @param frequency frequency to modulate in Hz.
      * @param ms duration of the pitch in milli seconds.
      */
@@ -322,7 +322,7 @@ namespace pins {
 
 
     /**
-    * Configure the pull directiion of of a pin.
+    * Configure the pull direction of of a pin.
     * @param name pin to set the pull mode on, eg: DigitalPin.P0
     * @param pull one of the mbed pull configurations, eg: PinPullMode.PullUp
     */