Add print(signed char | short | float) explicitly

Add explicit print() support for signed char, unsigned/signed short, and float.
Also, add `signed` keyword explicitly to int and long (even if unnecessary).

Notice that `char` and `signed char` are considered different types,
even if their ranges are the same (ditto for `unsigned char` in SAM).
Both AVR and SAM seem to define [u]int8_t explicitly as [un]signed char
and not as char, so printing them will print them as numbers as expected.
(This does not apply to `int` and `signed int`; those are the same type.)

Author: cousteaulecommandant

cores/arduino/Print.cpp

@@ -59,7 +59,7 @@ size_t Print::print(const String &s)
   return write(s.c_str(), s.length());
 }
 
-size_t Print::print(long n, int base)
+size_t Print::print(signed long n, int base)
 {
   if (base == 0) {
     return write(n);

cores/arduino/Print.h

@@ -64,17 +64,21 @@ class Print
 
     size_t print(const __FlashStringHelper *);
     size_t print(const String &);
-    size_t print(long, int = DEC);
+    size_t print(  signed long, int = DEC);
     size_t print(unsigned long, int = DEC);
     size_t print(double, int = 2);
 
     size_t print(const char str[])   { return write(str); }
     size_t print(const char c)       { return write(c); }
     size_t print(const Printable &x) { return x.printTo(*this); }
 
+    size_t print(  signed char  n, int f = DEC) { return print((  signed long) n, f); }
+    size_t print(  signed short n, int f = DEC) { return print((  signed long) n, f); }
+    size_t print(  signed int   n, int f = DEC) { return print((  signed long) n, f); }
     size_t print(unsigned char  n, int f = DEC) { return print((unsigned long) n, f); }
-    size_t print(         int   n, int f = DEC) { return print((         long) n, f); }
+    size_t print(unsigned short n, int f = DEC) { return print((unsigned long) n, f); }
     size_t print(unsigned int   n, int f = DEC) { return print((unsigned long) n, f); }
+    size_t print(    float      n, int f = 2  ) { return print((    double   ) n, f); }
 
     size_t println(void);