Updated CHANGELOG and VARIANT_COMPLIANCE_CHANGELOG

CHANGELOG

+SAMD CORE 1.6.10 2016.12.23
+
+* Added .org boards
+* Fixed MKRZero `build.board` property
+* linker: .data section is now aligned to 16 bytes address
+* Added support for CRYSTALLESS configurations (thanks @ladyada)
+* Added Circuits Playground board
+* Added method to automatically retrieve sketch start via linker variable
+  (see https://github.com/arduino/ArduinoCore-samd/pull/185)
+* Fixed USBDevice.epBank1EnableTransferComplete method
+* Adapted bootloader source code to CMSIS 4.5
+
 SAMD CORE 1.6.9 2016.12.12
 
 * MKR1000: Enabled PWM on pin 11, it is shared with pin A4

VARIANT_COMPLIANCE_CHANGELOG

 SAMD CORE 1.6.10
 
-* the linker script is use should define __text_start__ symbol at the beginning of .text section
+* The linker script must define `__text_start__` symbol at the beginning of .text section.
+  This symbol is used to automatically determine the bootloader size.
 
 SAMD CORE 1.6.6
 
-* digitalPinToInterrupt #define moved to Arduino.h, variant.h must no longer define it
+* `digitalPinToInterrupt` #define moved to Arduino.h, variant.h must no longer define it.
 
 SAMD CORE 1.6.3
 
-* Timer for pin PWM selected based on value of PIN_ATTR_TIMER_ALT or PIN_ATTR_TIMER,
-  prior to this "pin type" (ulPinType) was used
+* Timer for pin PWM selected based on value of `PIN_ATTR_TIMER_ALT` or `PIN_ATTR_TIMER`.
+  Prior to this "pin type" (ulPinType) was used.