regen/embed.pl: A,C and either [EX] flags are mutually exclusive

It makes no sense to specify more than one of A C X, nor more than one
of A C E.  This commit enforces that, showing one entry in embed.fnc
that needed to be changed.

Author: khwilliamson

embed.fnc

@@ -2074,7 +2074,7 @@ Cp	|const char *|moreswitches					\
 Adp	|void	|mortal_destructor_sv					\
 				|NN SV *coderef 			\
 				|NULLOK SV *args
-CRTXip	|char * |mortal_getenv	|NN const char *str
+CRTip	|char * |mortal_getenv	|NN const char *str
 Cdp	|void	|mortal_svfunc_x|SVFUNC_t f				\
 				|NULLOK SV *p
 Adop	|const struct mro_alg *|mro_get_from_name			\

regen/embed.pl

@@ -143,6 +143,12 @@ sub generate_proto_h {
             warn "It is nonsensical to require the return value of a void function ($plain_func) to be checked";
         }
 
+        my $has_E_or_X = $flags =~ /[EX]/;
+        if ($has_E_or_X + ($flags =~ tr/AC//) > 1) {
+            die_at_end "$plain_func: A, C, and either E or X flags are"
+                     . " mutually exclusive";
+        }
+
         die_at_end "$plain_func: S and p flags are mutually exclusive"
                                                     if $flags =~ tr/Sp// > 1;
         if ($has_mflag) {