Revert "Disabled RTTI and exceptions."

RTTI causes linking problems in depending projects and it's not
desirable to force them all to not use it. Exceptions are used by
the new TestSuite in Corrade, so they must be also enabled.

This reverts commit eb82cb462a.

Conflicts:
	src/CMakeLists.txt

src/CMakeLists.txt

@@ -1,4 +1,4 @@
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Wold-style-cast -pedantic -std=c++0x -fvisibility=hidden -fno-rtti -fno-exceptions")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Wold-style-cast -pedantic -std=c++0x -fvisibility=hidden")
 
 if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wdouble-promotion")