Makefile.defs: version set to 5.2.0-pre0

- code in master branch is frozen - no new features till branching 5.2
- start of testing period

src/Makefile.defs

@@ -107,7 +107,7 @@ INSTALL_FLAVOUR=$(FLAVOUR)
 VERSION = 5
 PATCHLEVEL = 2
 SUBLEVEL =  0
-EXTRAVERSION = -dev9
+EXTRAVERSION = -pre0
 
 # memory manager switcher
 # 0 - f_malloc (fast malloc)