Simplify header install locations

Everything goes in
<prefix>/include/KF*/KSyntaxHighlighting/KSyntaxHighlighting

With <prefix>/include/KF*/KSyntaxHighlighting added to the target interface
include directories.

This is simpler, should work with case-insensitive (and/or case-preserving
filesystems), and should work with KF6 without having to add <prefix>/include/KF*/
to the target include dirs via ECM to all KF repos.

src/lib/CMakeLists.txt

@@ -72,35 +72,17 @@ set(Forwarding_Header_Names
 ecm_generate_headers(CamelCase_HEADERS
     HEADER_NAMES ${Forwarding_Header_Names}
     REQUIRED_HEADERS SyntaxHighlighting_HEADERS
-    PREFIX KSyntaxHighlighting
 )
 
 install(TARGETS KF5SyntaxHighlighting EXPORT KF5SyntaxHighlightingTargets ${KDE_INSTALL_TARGETS_DEFAULT_ARGS})
 
 install(FILES
     ${CamelCase_HEADERS}
-    DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF}/KSyntaxHighlighting/KSyntaxHighlighting
-)
-install(FILES
     ${SyntaxHighlighting_HEADERS}
     ${CMAKE_CURRENT_BINARY_DIR}/ksyntaxhighlighting_export.h
-    DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF}/KSyntaxHighlighting/ksyntaxhighlighting
+    DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF}/KSyntaxHighlighting/KSyntaxHighlighting
 )
 
-# TODO KF6: remove this, backward compatible headers location
-if(QT_MAJOR_VERSION STREQUAL "5")
-    ecm_generate_headers(Compat_CamelCase_HEADERS
-        HEADER_NAMES ${Forwarding_Header_Names}
-        REQUIRED_HEADERS Compat_SyntaxHighlighting_HEADERS
-    )
-    install(FILES
-        ${Compat_CamelCase_HEADERS}
-        ${Compat_SyntaxHighlighting_HEADERS}
-        ${CMAKE_CURRENT_BINARY_DIR}/ksyntaxhighlighting_export.h
-        DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF}/KSyntaxHighlighting
-    )
-endif()
-
 if(BUILD_QCH)
     ecm_add_qch(
         KF5SyntaxHighlighting_QCH