Update README_DEVELOPERS and references to --vex-guest-chase-thresh.

Add a hint about using lldb in README_DEVELOPERS and fix any old references
to --vex-guest-chase-thresh=0 to --vex-guest-chase=no (mirroring the change
in commit 56e04256a "Rationalise --vex-guest* flags in the new IRSB
construction framework".

Reported-by: Paul FLOYD <pjfloyd@wanadoo.fr>

README_DEVELOPERS

@@ -110,6 +110,10 @@ without too much problem by following these steps:
 
     (gdb) handle SIGILL SIGSEGV nostop noprint
 
+    If you are using lldb, then the equivalent command is
+
+    (lldb) pro hand -p true -s false -n false SIGILL SIGSEGV
+
 (4) Set any breakpoints you want and proceed as normal for gdb. The
     macro VG_(FUNC) is expanded to vgPlain_FUNC, so If you want to set
     a breakpoint VG_(do_exec), you could do like this in GDB:
@@ -327,7 +331,7 @@ Printing out problematic blocks
 If you want to print out a disassembly of a particular block that
 causes a crash, do the following.
 
-Try running with "--vex-guest-chase-thresh=0 --trace-flags=10000000
+Try running with "--vex-guest-chase=no --trace-flags=10000000
 --trace-notbelow=999999".  This should print one line for each block
 translated, and that includes the address.
 

exp-bbv/docs/bbv-manual.xml

@@ -263,7 +263,7 @@ T:18:45 :12:135353 :56:78 314:4324263]]></programlisting>
    BBV vectors will be different than those generated by other tools.
    In practice this does not seem to affect the accuracy of the
    SimPoint results.  We do internally force the
-   <option>--vex-guest-chase-thresh=0</option>
+   <option>--vex-guest-chase=no</option>
    option to Valgrind which forces a more basic-block-like
    behavior.
 </para>

lackey/lk_main.c

@@ -739,7 +739,7 @@ IRSB* lk_instrument ( VgCallbackClosure* closure,
                 * instrument, by the VEX statements that are the
                 * translation of that known destination. This feature is
                 * called 'SB chasing' and can be influenced by command
-                * line option --vex-guest-chase-thresh.
+                * line option --vex-guest-chase=[yes|no].
                 *
                 * To get an accurate count of the calls to a specific
                 * function, taking SB chasing into account, we need to