Allow toggling CRe's new dithering & scaling (#888)

Plus, implement said dithering in our own BB code, for ImageWidget

* A "few" buildsystem tweaks:
  * Use a real CMake ToolChain filme when cross-compiling, instead of piling on hacks
  * Export CC/CFLAGS & co to avoid having to daisy-chain those around, and make sure they'll always be honored.
    Actually getting rid of those in Makefile.third is left as an excerise to the reader ;).
    (Or, deferred to the next time a dep is bumped ;)).
  * Fixed distclean in base to actaully clean third party builds.
  * Honor VERBOSE in the env to switch to slightly more verbose builds
  * Fixed MACHINE shenanigans to behave properly, no matter what.
  * Made sure every toolchain was switched to at least C11/C++11
  * Got rid of those annoying hard-coded --silent build flags. Ninja is silent by default.

* Cleaned up jpeg-turbo CMake file
* Bumped LuaSec to 0.8
* Bumped OpenSSL to 1.1.1b

.travis.yml

@@ -55,3 +55,4 @@ install:
 script:
   - if [ "$SHELLCHECKS" = 1 ]; then source .ci/lint_script.sh; else source .ci/build_script.sh; fi
   - if [ "$EMULATE_READER" = 1 ]; then source .ci/test_script.sh; fi
+

Makefile

@@ -122,7 +122,7 @@ endif
 $(OUTPUT_DIR)/libs/libkoreader-cre.so: cre.cpp \
 			$(if $(USE_LUAJIT_LIB),$(LUAJIT_LIB),) \
 			$(CRENGINE_LIB)
-	$(CXX) -I$(CRENGINE_SRC_DIR)/crengine/include/ $(DYNLIB_CFLAGS) \
+	$(CXX) -I$(CRENGINE_SRC_DIR)/crengine/include/ $(DYNLIB_CXXFLAGS) \
 		-DLDOM_USE_OWN_MEM_MAN=$(if $(WIN32),0,1) \
 		$(if $(WIN32),-DQT_GL=1) -static-libstdc++ -o $@ $^
 ifdef DARWIN
@@ -189,7 +189,7 @@ clean:
 	-rm -rf $(OUTPUT_DIR)/*
 	-rm -rf $(THIRDPARTY_DIR)/{$(CMAKE_THIRDPARTY_LIBS)}/build/$(MACHINE)
 
-dist-clean:
+distclean:
 	-rm -rf build
 	-rm -rf $(THIRDPARTY_DIR)/{$(CMAKE_THIRDPARTY_LIBS)}/build
 
@@ -212,4 +212,4 @@ test: $(OUTPUT_DIR)/spec $(OUTPUT_DIR)/.busted
 		--no-auto-insulate \
 		-o ./spec/base/unit/verbose_print ./spec/base/unit
 
-.PHONY: all clean test
+.PHONY: all android-toolchain pocketbook-toolchain clean distclean test