Fix 64Bit Cyclotomic Size limit

Add test case for 2^32

Adjust test for 32bit systems

doc/ref/cyclotom.xml

@@ -202,7 +202,7 @@ This can be raised (although not lowered) using
 <Ref Func="SetCyclotomicsLimit"/> and
 accessed using <Ref Func="GetCyclotomicsLimit"/>.
 The maximum value of the limit is <M>2^{28}-1</M> on <M>32</M> bit systems,
-and <M>2^{32}</M> on <M>64</M> bit systems.
+and <M>2^{32}-1</M> on <M>64</M> bit systems.
 So the maximal cyclotomic field implemented in &GAP; is not really
 the field <M>&QQ;^{ab}</M>.
 <P/>

src/cyclotom.c

@@ -854,7 +854,7 @@ static Obj FuncSetCyclotomicsLimit(Obj self, Obj newlimit)
                      CyclotomicsLimit, 0);
     }
 #ifdef SYS_IS_64_BIT
-    if (ulimit > (1L << 32)) {
+    if (ulimit >= (1L << 32)) {
         ErrorMayQuit("Cyclotomic field size limit must be less than 2^32", 0,
                      0);
     }

tst/testinstall/cyclotom.tst

@@ -276,6 +276,10 @@ he integer 0)
 gap> SetCyclotomicsLimit(100);
 Error, SetCyclotomicsLimit: <newlimit> must not be less than old limit of 1000\
 000
+#@if 8*GAPInfo.BytesPerVariable = 64
+gap> SetCyclotomicsLimit(2^32);
+Error, Cyclotomic field size limit must be less than 2^32
+#@fi
 gap> SetCyclotomicsLimit(1000000);
 
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