Enable config=sanitize in Travis CI

This commit changes sanitize configuration to fail on the first error
and ignore floating-point division and overflow "errors" that trigger
when we test the corresponding functionality. This makes it possible to
run this on all commits - if new UB or memory safety issues are introduced,
asan/ubsan will catch them.

.travis.yml

@@ -18,6 +18,7 @@ env:
   - DEFINES=PUGIXML_NO_EXCEPTIONS
 script:
   - make test cxxstd=c++11 defines=$DEFINES config=coverage -j2
+  - if [[ "$CXX" == "clang++" ]]; then make test cxxstd=c++11 defines=$DEFINES config=sanitize -j2; fi
   - make test cxxstd=c++11 defines=$DEFINES config=release -j2
   - make test cxxstd=c++98 defines=$DEFINES config=debug -j2
 

Makefile

@@ -27,7 +27,7 @@ ifeq ($(config),coverage)
 endif
 
 ifeq ($(config),sanitize)
-	CXXFLAGS+=-fsanitize=address,undefined
+	CXXFLAGS+=-fsanitize=address,undefined -fno-sanitize=float-divide-by-zero,float-cast-overflow -fno-sanitize-recover=all
 	LDFLAGS+=-fsanitize=address,undefined
 endif