renaming DNN options in meson #558

Job	Run time
CMake MINGW	1m 0s
Test build with CMake 3.1.0	1m 15s
CMake/Android/So/ARMv8/Release	48s
CMake/Android/So/X86/Release	37s
CMake/Android/So/X64/Release	37s
CMake/Windows/Dll/X86/Release	1m 43s
CMake/Windows/Dll/X64/Release	2m 20s
CMake/Windows/Dll/ARMv8/Release	59s
CMake/Linux/So/X64/Release	23s
CMake/MacOSX/So/X64/Release	47s
CMake/MacOSX/Framework/X64/Release	1m 32s
CMake/iOS/Dll/arm64/Release	55s
CMake/iOS/Framework/arm64/Release	47s
CMake/Windows/Lib/X86/Release	2m 56s
CMake/Windows/Lib/X64/Release	2m 26s
CMake/Windows/Lib/armv8/Release	1m 39s
CMake/Linux/Lib/X64/Release	1m 36s
CMake/MacOSX/Lib/X64/Release	1m 20s
CMake/iOS/Lib/arm64/Release	49s
CMake/Android/Lib/ARMv8/Release	45s
CMake/Android/Lib/X86/Release	49s
CMake/Android/Lib/X64/Release	50s
CMake/CustomModes/Linux/Lib/X64/Release	1m 2s
CMake/AssertionsFuzz/Windows/Lib/X64/Release	2m 9s
CMake/AssertionsFuzz/Linux/Lib/X64/Release	1m 5s
CMake/AssertionsFuzz/MacOSX/Lib/X64/Release	1m 29s
	32m 38s

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