Libraries: Add missing includes, add namespace qualifiers

This remained undetected for a long time as HeaderCheck is disabled by
default. This commit makes the following file compile again:

    // file: compile_me.cpp
    #include <LibDNS/Question.h>
    // That's it, this was enough to cause a compilation error.

Likewise for most other files touched by this commit.

Userland/Libraries/LibCodeComprehension/Shell/ConnectionFromClient.h

@@ -19,7 +19,7 @@ private:
     ConnectionFromClient(NonnullOwnPtr<Core::Stream::LocalSocket> socket)
         : LanguageServers::ConnectionFromClient(move(socket))
     {
-        m_autocomplete_engine = make<ShellComprehensionEngine>(m_filedb);
+        m_autocomplete_engine = make<CodeComprehension::Shell::ShellComprehensionEngine>(m_filedb);
         m_autocomplete_engine->set_declarations_of_document_callback = [this](String const& filename, Vector<CodeComprehension::Declaration>&& declarations) {
             async_declarations_in_document(filename, move(declarations));
         };

Userland/Libraries/LibDNS/Question.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include "Answer.h"
 #include "Name.h"
 #include <AK/Types.h>
 

Userland/Libraries/LibGPU/StencilConfiguration.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <LibGPU/Config.h>
 #include <LibGPU/Enums.h>
 
 namespace GPU {

Userland/Libraries/LibGfx/Font/VectorFont.h

@@ -8,6 +8,7 @@
 
 #include <AK/Noncopyable.h>
 #include <AK/RefCounted.h>
+#include <LibGfx/Forward.h>
 
 namespace Gfx {
 

Userland/Libraries/LibGfx/PNGShared.h

@@ -6,6 +6,9 @@
 
 #pragma once
 
+#include <AK/Array.h>
+#include <AK/SIMD.h>
+
 namespace Gfx::PNG {
 
 // https://www.w3.org/TR/PNG/#5PNG-file-signature
@@ -33,9 +36,9 @@ enum class FilterType : u8 {
 ALWAYS_INLINE u8 paeth_predictor(u8 a, u8 b, u8 c)
 {
     int p = a + b - c;
-    int pa = abs(p - a);
-    int pb = abs(p - b);
-    int pc = abs(p - c);
+    int pa = AK::abs(p - a);
+    int pb = AK::abs(p - b);
+    int pc = AK::abs(p - c);
     if (pa <= pb && pa <= pc)
         return a;
     if (pb <= pc)

Userland/Libraries/LibIPC/Encoder.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/Concepts.h>
+#include <AK/HashMap.h>
 #include <AK/StdLibExtras.h>
 #include <LibCore/SharedCircularQueue.h>
 #include <LibIPC/Forward.h>

Userland/Libraries/LibLine/Style.h

@@ -8,6 +8,7 @@
 
 #include <AK/String.h>
 #include <AK/Types.h>
+#include <AK/Utf8View.h>
 #include <AK/Vector.h>
 #include <stdlib.h>
 

Userland/Libraries/LibPDF/XRefTable.h

@@ -10,6 +10,7 @@
 #include <AK/RefCounted.h>
 #include <AK/String.h>
 #include <AK/Vector.h>
+#include <LibPDF/Error.h>
 
 namespace PDF {
 

Userland/Libraries/LibSoftGPU/SIMD.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/SIMDExtras.h>
+#include <AK/SIMDMath.h>
 #include <LibGfx/Vector2.h>
 #include <LibGfx/Vector3.h>
 #include <LibGfx/Vector4.h>

Userland/Libraries/LibXML/DOM/Node.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/HashMap.h>
 #include <AK/NonnullOwnPtrVector.h>
 #include <AK/String.h>
 #include <AK/Variant.h>