enum may be signed

[grischka]

In git:2f2ce26ff273aadaf324ec599bf1dd1f67cab560 (Stefan Monnier)

+enum symbol_redirect
+{
+  SYMBOL_PLAINVAL  = 4,
...

 struct Lisp_Symbol
 {
   unsigned gcmarkbit : 1;
...
+  enum symbol_redirect redirect : 3;


Note that this breaks with compilers where enums can be signed (e.g. MSVC),
Because value 4 doesn't fit into 3 bits (signed), it is read as -4 and
breaks related switch statements (e.g. data.c:set_internal)

--- grischka