ReSTART fix, Sequencing fix

pr espressif#1665 introduce a problem with ReSTART, when solving this problem I found an interaction between the TxFifo refill, RxFifo empty and CMD[] fill.  during certain sequences a dataqueue command would be skipped, this skipping resulted in a mismatch between the contents of the TxFifo and the i2c command sequence.  The problem manifested as an ACK error. 
In addition to this required bug fix I propose:
* `Wire.begin()` be changed from a `void` to a `bool` this will allow the reset functionality of `Wire.begin()` to be reported.  Currently `Wire.begin()` attempts to reset the i2c Peripheral, but cannot report success/failure.
* `Wire.busy()` be added. this `bool` function returns the hardware status of the bus. This status can be use in multi-master environments for application level interleaving of commands, also in single master environment, it can be used to detect a 'hung' bus.  With the functional change to `Wire.begin()` this allows app level recover of a hung bus.
* `Wire.lastError()` value updated for all errors, previously when interleaving `Wire.endTransmission(false)` and `Wire.readTransmission(false)`, the 128 byte `Wire.write()` buffer was exhausted without generating and error(very exotic). I discovered this error when I created a sequence of directed reads to a EEPROM. Each directed read used 2 bytes of the 128 byte `write()` buffer, so after 64 consecutive ReSTART writes with ReSTART reads, `Wire()`  had no room to record the directed address bytes.  It generated just a NAK check without setting the EEPROMs internal register address.  The succeeding ReSTART read succeeded at incorrect address.
* Changes to the HAL layer:
** added `i2cGetStatus()` which returns the i2c peripheral status word, used to detect bus_busy currently
** added `i2cDebug()` programmatic control of debug buffer output
** changed `i2cAddQueue()` to allow data_only queue element this will allow a i2c transaction to use multiple data pointers.
** removed direct access to DumpInts(), DumpI2c() from app, use i2cDebug() to set trigger points 
 
*

Author: stickbreaker

cores/esp32/esp32-hal-i2c.h

@@ -48,6 +48,7 @@ i2c_err_t i2cRead(i2c_t * i2c, uint16_t address, uint8_t* buff, uint16_t size, b
 i2c_err_t i2cFlush(i2c_t *i2c);
 i2c_err_t i2cSetFrequency(i2c_t * i2c, uint32_t clk_speed);
 uint32_t i2cGetFrequency(i2c_t * i2c);
+uint32_t i2cGetStatus(i2c_t * i2c); // Status register of peripheral
 
 //Functions below should be used only if well understood
 //Might be deprecated and removed in future
@@ -62,8 +63,17 @@ i2c_err_t i2cAddQueueWrite(i2c_t *i2c, uint16_t i2cDeviceAddr, uint8_t *dataPtr,
 i2c_err_t i2cAddQueueRead(i2c_t *i2c, uint16_t i2cDeviceAddr, uint8_t *dataPtr, uint16_t dataLen, bool SendStop, EventGroupHandle_t event);
 
 //stickbreaker debug support
-void i2cDumpInts(uint8_t num);
-void i2cDumpI2c(i2c_t *i2c);
+uint32_t i2cDebug(i2c_t *, uint32_t setBits, uint32_t resetBits);
+//  Debug actions have 3 currently defined locus 
+// 0xXX------ : at entry of ProcQueue 
+// 0x--XX---- : at exit of ProcQueue
+// 0x------XX : at entry of Flush
+// 
+// bit 0 causes DumpI2c to execute 
+// bit 1 causes DumpInts to execute
+// bit 2 causes DumpCmdqueue to execute
+// bit 3 causes DumpStatus to execute
+// bit 4 causes DumpFifo to execute
 
 #ifdef __cplusplus
 }