Remove some definitions from global namespace

Names like kB, MB and kHz are likely to collide with variable names in user sketches.
Nowadays this should be implemented using c++14 user-defined literals (http://en.cppreference.com/w/cpp/language/user_literal)

Author: igrr

hardware/esp8266com/esp8266/cores/esp8266/Arduino.h

@@ -82,18 +82,6 @@ void yield(void);
 #define degrees(rad) ((rad)*RAD_TO_DEG)
 #define sq(x) ((x)*(x))
 
-#define kHz (1000L)
-#define MHz (1000L*kHz)
-#define GHz (1000L*MHz)
-
-#define kBit (1024L)
-#define MBit (1024L*kBit)
-#define GBit (1024L*MBit)
-
-#define kB (1024L)
-#define MB (1024L*kB)
-#define GB (1024L*MB)
-
 void ets_intr_lock();
 void ets_intr_unlock();
 

hardware/esp8266com/esp8266/cores/esp8266/Esp.cpp

@@ -24,6 +24,17 @@ extern "C" {
 #include "user_interface.h"
 }
 
+#define kHz (1000L)
+#define MHz (1000L*kHz)
+#define GHz (1000L*MHz)
+
+#define kBit (1024L)
+#define MBit (1024L*kBit)
+#define GBit (1024L*MBit)
+
+#define kB (1024L)
+#define MB (1024L*kB)
+#define GB (1024L*MB)
 
 //extern "C" void ets_wdt_init(uint32_t val);
 extern "C" void ets_wdt_enable(void);