AK: Remove the ctype adapters and use the actual ctype functions instead

This finally takes care of the kind-of excessive boilerplate code that were the
ctype adapters. On the other hand, I had to link `LibC/ctype.cpp` to the Kernel
(for `AK/JsonParser.cpp` and `AK/Format.cpp`). The previous commit actually makes
sense now: the `string.h` includes in `ctype.{h,cpp}` would require to link more LibC
stuff to the Kernel when it only needs the `_ctype_` array of `ctype.cpp`, and there
wasn't any string stuff used in ctype.
Instead of all this I could have put static derivatives of `is_any_of()` in the
concerned AK files, however that would have meant more boilerplate and workarounds;
so I went for the Kernel approach.

Kernel/CMakeLists.txt

@@ -223,7 +223,6 @@ set(VT_SOURCES
     ../Libraries/LibVT/Line.cpp
 )
 
-
 set(KEYBOARD_SOURCES
     ../Libraries/LibKeyboard/CharacterMap.cpp
 )
@@ -233,6 +232,10 @@ set(CRYPTO_SOURCES
     ../Libraries/LibCrypto/Hash/SHA2.cpp
 )
 
+set(C_SOURCES
+    ../Libraries/LibC/ctype.cpp
+)
+
 set(SOURCES
     ${KERNEL_SOURCES}
     ${AK_SOURCES}
@@ -240,6 +243,7 @@ set(SOURCES
     ${VT_SOURCES}
     ${KEYBOARD_SOURCES}
     ${CRYPTO_SOURCES}
+    ${C_SOURCES}
 )
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unknown-warning-option -DKERNEL")