Update libcurl from 7.54.1 to 7.55.1.

Bug: http://b/64610131
Test: builds, boots, `vendor/google/tools/fake-ota on streaming` works
Change-Id: I7ecaf9c83e9496ac4a379507791bec637deaa4cb
diff --git a/src/tool_formparse.c b/src/tool_formparse.c
index 88352fb..952377c 100644
--- a/src/tool_formparse.c
+++ b/src/tool_formparse.c
@@ -28,6 +28,7 @@
 #include "curlx.h"
 
 #include "tool_cfgable.h"
+#include "tool_convert.h"
 #include "tool_mfiles.h"
 #include "tool_msgs.h"
 #include "tool_formparse.h"
@@ -153,7 +154,7 @@
   char type_major[128] = "";
   char type_minor[128] = "";
   char *contp;
-  const char *type = NULL;
+  char *type = NULL;
   char *sep;
 
   if((1 == sscanf(input, "%255[^=]=", name)) &&
@@ -214,7 +215,7 @@
             }
 
             /* now point beyond the content-type specifier */
-            sep = (char *)type + strlen(type_major)+strlen(type_minor)+1;
+            sep = type + strlen(type_major)+strlen(type_minor)+1;
 
             /* there's a semicolon following - we check if it is a filename
                specified and if not we simply assume that it is text that