Configure: use -Wstrict-aliasing -Wstrict-overflow

configure.ac

@@ -28,7 +28,7 @@ AC_PROG_CC_C99
 AM_PROG_CC_C_O
 
 dnl check for -Wall -Wextra support
-CC_CHECK_CFLAG_APPEND([-Wall -Wsign-compare -Wextra])
+CC_CHECK_CFLAG_APPEND([-Wall -Wsign-compare -Wextra -Wstrict-aliasing -Wstrict-overflow])
 
 dnl Where is iconv? In libc or separate lib?
 AM_ICONV