Bug 1686831 - Add support for %F and %G, and properly support %n$E. r=nika,Gankra

%F and %G are the same as %f and %g, but using caps for the exponent
indicator, and for "inf"/"nan" for infinity and NaN.

%n$E is the same as %E, but taking the nth argument.

Differential Revision: https://phabricator.services.mozilla.com/D102695

mozglue/misc/Printf.cpp

@@ -491,8 +491,11 @@ static bool BuildArgArray(const char* fmt, va_list ap, NumArgStateVector& nas) {
         break;
 
       case 'e':
+      case 'E':
       case 'f':
+      case 'F':
       case 'g':
+      case 'G':
         nas[cn].type = TYPE_DOUBLE;
         break;
 
@@ -825,7 +828,9 @@ bool mozilla::PrintfTarget::vprint(const char* fmt, va_list ap) {
       case 'e':
       case 'E':
       case 'f':
+      case 'F':
       case 'g':
+      case 'G':
         u.d = va_arg(ap, double);
         if (!nas.empty()) {
           i = fmt - dolPt;