Fix WITH_DEBUG problems in CMake build, so people who use configure wrappers do not

suffer. The problem was that when custom C flags were defined with in environment 
variable CFLAGS, WITH_DEBUG did not have any effect. Also, switch from 
WITH_DEBUG=ON to WITH_DEBUG=OFF   was not handled correctly .Expected is switch 
to with RelwithDebInfo or when custom compiler flags  are defined, to None.

CMakeLists.txt

@@ -32,26 +32,32 @@ IF(DEFINED CMAKE_BUILD_TYPE)
   SET(HAVE_CMAKE_BUILD_TYPE TRUE)
 ENDIF()
 SET(CUSTOM_C_FLAGS $ENV{CFLAGS})
-IF(NOT CUSTOM_C_FLAGS)
-  SET(CUSTOM_C_FLAGS ${CMAKE_C_FLAGS})
-ENDIF()
 
-OPTION(WITH_DEBUG "Use dbug" OFF)
+OPTION(WITH_DEBUG "Use dbug/safemutex" OFF)
 OPTION(WITH_DEBUG_FULL "Use dbug and safemalloc/safemutex. Slow" OFF)
 
-IF(NOT HAVE_CMAKE_BUILD_TYPE)
-   IF(BUILD_CONFIG OR NOT CUSTOM_C_FLAGS)
-     IF(WITH_DEBUG)
-       SET(CMAKE_BUILD_TYPE "Debug" CACHE STRING "Debug build" FORCE)
-     ELSE()
+
+# We choose to provide WITH_DEBUG as alias to standard CMAKE_BUILD_TYPE=Debug
+# which turns out to be not trivial, as this involves synchronization 
+# between CMAKE_BUILD_TYPE and WITH_DEBUG. Besides, we have to deal with cases
+# where WITH_DEBUG is  reset from ON to OFF  and here we need to reset 
+# CMAKE_BUILD_TYPE to either none or default RelWithDebInfo
+
+SET(BUILDTYPE_DOCSTRING
+ "Choose the type of build, options are: None(CMAKE_CXX_FLAGS or
+ CMAKE_C_FLAGS used) Debug Release RelWithDebInfo MinSizeRel")
+ 
+IF(WITH_DEBUG OR WITH_DEBUG_FULL)
+  SET(CMAKE_BUILD_TYPE "Debug" CACHE STRING ${BUILDTYPE_DOCSTRING} FORCE)
+  SET(OLD_WITH_DEBUG 1 CACHE INTERNAL "" FORCE)
+ELSEIF(NOT HAVE_CMAKE_BUILD_TYPE OR OLD_WITH_DEBUG)
+  IF(CUSTOM_C_FLAGS)
+    SET(CMAKE_BUILD_TYPE "" CACHE STRING ${BUILDTYPE_DOCSTRING} FORCE)
+  ELSE(CMAKE_BUILD_TYPE MATCHES "Debug" OR NOT HAVE_CMAKE_BUILD_TYPE)
     SET(CMAKE_BUILD_TYPE "RelWithDebInfo" CACHE STRING 
-        "RelWithDebInfo build" FORCE)
-     ENDIF()
+       ${BUILDTYPE_DOCSTRING} FORCE)
   ENDIF()
-ENDIF()
-
-IF(WITH_DEBUG_FULL)
-  SET(WITH_DEBUG ON CACHE BOOL "Use DBUG")
+  SET(OLD_WITH_DEBUG 0 CACHE INTERNAL "" FORCE)
 ENDIF()
 
 IF(BUILD_CONFIG)