vmodtool: Add option to specify c names of arguments and avoid "bool"

I tried gcc version 15.0.0 20241203 and even without -std=c23, it would reserve
"bool":

In file included from vcc_std_if.c:10:
vcc_std_if.h:78:33: error: two or more data types in declaration specifiers
   78 |         VCL_BOOL                bool;
      |                                 ^~~~

(and more)

So this patch adds the option to specify the c name of arguments to vmod
functions/methods by separating it with a colon:

	vclname:cname

We use this facility to rename the "bool" argument to vmod_std functions to
"boola".

lib/libvcc/vmodtool.py

@@ -385,6 +385,8 @@ def __init__(self, st, retval=True, prefix=""):
                 err("arguments cannot be of type '%s'" % t.vt, warn=False)
             if t.nm is None:
                 t.nm2 = "arg%d" % n
+            elif ':' in t.nm:
+                [t.nm, t.nm2] = t.nm.split(':')
             else:
                 t.nm2 = t.nm
             self.args.append(t)

vmod/vmod_std.vcc

@@ -308,7 +308,7 @@ Example::
 	std.cache_req_body(std.bytes(real=10.0*1024));
 
 $Function INT integer([STRING s], [INT fallback],
-    [BOOL bool], [BYTES bytes], [DURATION duration], [REAL real],
+    [BOOL bool:boola], [BYTES bytes], [DURATION duration], [REAL real],
     [TIME time])
 
 Returns an INT from a STRING, BOOL or other quantity.
@@ -376,7 +376,7 @@ Example::
 	}
 
 $Function REAL real([STRING s], [REAL fallback], [INT integer],
-    [BOOL bool], [BYTES bytes], [DURATION duration],
+    [BOOL bool:boola], [BYTES bytes], [DURATION duration],
     [TIME time])
 
 Returns a REAL from a STRING, BOOL or other quantity.

vmod/vmod_std_conversions.c

@@ -157,7 +157,7 @@ vmod_integer(VRT_CTX, struct VARGS(integer) *a)
 
 	r = NAN;
 	if (a->valid_bool)
-		return (a->bool ? 1 : 0);
+		return (a->boola ? 1 : 0);
 
 	if (a->valid_bytes)
 		return (a->bytes);
@@ -255,7 +255,7 @@ vmod_real(VRT_CTX, struct VARGS(real) *a)
 		return ((VCL_REAL)a->integer);
 
 	if (a->valid_bool)
-		return ((VCL_REAL)(a->bool ? 1 : 0));
+		return ((VCL_REAL)(a->boola ? 1 : 0));
 
 	if (a->valid_bytes)
 		return ((VCL_REAL)a->bytes);