GL: make the DynamicAttribute::Kind enum just 1 byte.

It's four values, 2 bits of information. No need to waste another 30.

src/Magnum/GL/Attribute.h

@@ -421,7 +421,7 @@ class MAGNUM_GL_EXPORT DynamicAttribute {
          * Specifies what kind of shader type matches the attribute.
          * @see @ref DynamicAttribute()
          */
-        enum class Kind {
+        enum class Kind: UnsignedByte {
             /** Generic, matches single-precision floating-point shader type */
             Generic,
 

src/Magnum/GL/Test/AttributeTest.cpp

@@ -1002,8 +1002,8 @@ void AttributeTest::debugDataTypeVector4() {
 
 void AttributeTest::debugDynamicKind() {
     std::ostringstream out;
-    Debug{&out} << DynamicAttribute::Kind::GenericNormalized << DynamicAttribute::Kind(0xdead);
-    CORRADE_COMPARE(out.str(), "GL::DynamicAttribute::Kind::GenericNormalized GL::DynamicAttribute::Kind(0xdead)\n");
+    Debug{&out} << DynamicAttribute::Kind::GenericNormalized << DynamicAttribute::Kind(0xfe);
+    CORRADE_COMPARE(out.str(), "GL::DynamicAttribute::Kind::GenericNormalized GL::DynamicAttribute::Kind(0xfe)\n");
 }
 
 void AttributeTest::debugDynamicComponents() {