dropbear: update to 2012.55 and refresh patches

Upstream has a few code cleanups, more eagerly burns sensitive memory and
includes the fix for CVE-2012-0920. Full changelog:
https://matt.ucc.asn.au/dropbear/CHANGES

Local changes:
- Removed PKG_MULTI which is no longer in options.h (even before 2011.54)
- Merged DO_HOST_LOOKUP into 120-openwrt_options.patch
- Removed LD from make opts (now included in TARGET_CONFIGURE_OPTS)
- Removed 400-CVE-2012-0920.patch which is included in 2012.55

Signed-off-by: Catalin Patulea <cat@vv.carleton.ca>
Signed-off-by: Florian Fainelli <florian@openwrt.org>

SVN-Revision: 34496

package/network/services/dropbear/patches/140-disable_assert.patch

@@ -1,6 +1,6 @@
 --- a/dbutil.h
 +++ b/dbutil.h
-@@ -94,6 +94,10 @@ int m_str_to_uint(const char* str, unsig
+@@ -93,6 +93,10 @@ int m_str_to_uint(const char* str, unsig
  #define DEF_MP_INT(X) mp_int X = {0, 0, 0, NULL}
  
  /* Dropbear assertion */