Math: fix warning about literal types in normalize().

C++11 changed type of character literal (i.e. '\x7F') from int to char,
thus the documentation is wrong (also mistakenly used octal literal).
Added test to properly test the behavior.

src/Math/Functions.h

@@ -231,11 +231,11 @@ value in range @f$ [0, 1] @f$ or from *signed* integral to range @f$ [-1, 1] @f$
     literals, this function should be called with both template parameters
     explicit, e.g.:
 @code
-// Even if this is character literal, integral type is 32bit, thus a != 1.0f
-float a = normalize<float>('\127');
+// Literal type is (signed) char, but we assumed unsigned char, a != 1.0f
+float a = normalize<float>('\xFF');
 
 // b = 1.0f
-float b = normalize<float, std::int8_t>('\127');
+float b = normalize<float, std::uint8_t>('\xFF');
 @endcode
 
 @see denormalize()

src/Math/Test/FunctionsTest.cpp

@@ -37,6 +37,8 @@ class FunctionsTest: public Corrade::TestSuite::Tester {
         void renormalizeUnsinged();
         void renormalizeSinged();
 
+        void normalizeTypeDeduction();
+
         void pow();
         void log();
         void log2();
@@ -65,6 +67,8 @@ FunctionsTest::FunctionsTest() {
              &FunctionsTest::renormalizeUnsinged,
              &FunctionsTest::renormalizeSinged,
 
+             &FunctionsTest::normalizeTypeDeduction,
+
              &FunctionsTest::pow,
              &FunctionsTest::log,
              &FunctionsTest::log2,
@@ -233,6 +237,11 @@ void FunctionsTest::renormalizeSinged() {
     CORRADE_COMPARE(Math::normalize<long double>(Math::denormalize<std::int64_t>(1.0l)), 1.0l);
 }
 
+void FunctionsTest::normalizeTypeDeduction() {
+    CORRADE_COMPARE(Math::normalize<float>('\x7F'), 1.0f);
+    CORRADE_COMPARE((Math::normalize<float, std::int8_t>('\x7F')), 1.0f);
+}
+
 void FunctionsTest::pow() {
     CORRADE_COMPARE(Math::pow<10>(2ul), 1024ul);
     CORRADE_COMPARE(Math::pow<0>(3ul), 1ul);