c: simplify integer mappings

`short` is perfectly fine as-is in C.

`qlonglong` is a bit trickier - Qt declares it to be `qint64` and
`qint64` to be `long long` - ergo, using `long long` in the C code is
fine but mapping `qint64` to `int64_t` actually might lead to trouble if
`int64_t` itself is not declared as `long long` (could be a mere `long
int` on some platforms) which in turn can lead to type-based pointer
aliasing violations :/ Ditto `qint32` vs `int32_t` which could be `int`
or `long`.

cmd/genbindings/emitcabi.go

@@ -105,10 +105,14 @@ func (p CppParameter) RenderTypeCabi() string {
 		return cabiClassName(p.ParameterType) + "*"
 	}
 
+	// https://github.com/qt/qtbase/blob/v5.15.16-lts-lgpl/src/corelib/global/qglobal.h#L233
+	// https://github.com/qt/qtbase/blob/v6.9.0/src/corelib/global/qtypes.h#L50
 	ret := p.ParameterType
 	switch p.ParameterType {
 	case "uchar":
 		ret = "unsigned char"
+	case "ushort":
+		ret = "unsigned short"
 	case "uint":
 		ret = "unsigned int"
 	case "ulong":
@@ -117,18 +121,22 @@ func (p CppParameter) RenderTypeCabi() string {
 		ret = "int8_t"
 	case "quint8":
 		ret = "uint8_t"
-	case "qint16", "short":
+	case "qint16":
 		ret = "int16_t"
-	case "quint16", "ushort", "unsigned short":
+	case "quint16":
 		ret = "uint16_t"
 	case "qint32":
 		ret = "int32_t"
 	case "quint32":
 		ret = "uint32_t"
-	case "qlonglong", "qint64":
+	case "qlonglong":
+		ret = "long long"
+	case "qint64":
 		ret = "int64_t"
-	case "qulonglong", "quint64":
+	case "quint64":
 		ret = "uint64_t"
+	case "qulonglong":
+		ret = "unsigned long long"
 	case "qfloat16":
 		ret = "_Float16" // No idea where this typedef comes from, but it exists
 	case "qreal":