Support to add unsigned long long and long long as fields

To be able to send large integers such as nanosecond timestamps for
syslog and Chronograf logging from esp32.

Currently casting to a smaller data type results in truncation, double
will not have the i suffix and casting to string (+"i") before calling
addField gets wrapped in quotation marks so database treats it as
string.

Fixes tobiasschuerg#164

src/Point.cpp

@@ -46,6 +46,18 @@ void Point::addTag(String name, String value) {
     _tags += escapeKey(value);
 }
 
+void Point::addField(String name, long long value) {
+  char buff[50];
+  snprintf(buff, 50, "%lld", value);
+  putField(name, String(buff)+"i");
+}
+
+void Point::addField(String name, unsigned long long value) {
+  char buff[50];
+  snprintf(buff, 50, "%llu", value);
+  putField(name, String(buff)+"i");
+}
+
 void Point::addField(String name, const char *value) { 
     putField(name, "\"" + escapeValue(value) + "\""); 
 }

src/Point.h

@@ -52,6 +52,8 @@ friend class InfluxDBClient;
     void addField(String name, unsigned long value) { putField(name, String(value)+"i"); }
     void addField(String name, bool value)          { putField(name, bool2string(value)); }
     void addField(String name, String value)        { addField(name, value.c_str()); }
+    void addField(String name, long long value);
+    void addField(String name, unsigned long long value);
     void addField(String name, const char *value);
     // Set timestamp to `now()` and store it in specified precision, nanoseconds by default. Date and time must be already set. See `configTime` in the device API
     void setTime(WritePrecision writePrecision = WritePrecision::NS);