FIX: making find case-insensitive by default on BITSET when used with a CHAR

resolves: Oldes/Rebol-issues#2166

Author: Oldes

src/core/t-bitset.c

@@ -600,7 +600,7 @@
 
 	case A_PICK:
 	case A_FIND:
-		if (!Check_Bits(VAL_SERIES(value), arg,(action == A_FIND && D_REF(ARG_FIND_CASE)) ))
+		if (!Check_Bits(VAL_SERIES(value), arg,(IS_CHAR(arg) && action == A_FIND && !D_REF(ARG_FIND_CASE)) ))
 #ifdef PICK_BITSET_AS_NONE
 			return R_NONE;
 #else

src/tests/units/bitset-test.r3

@@ -208,6 +208,24 @@
 ===end-group===
 
 
+===start-group=== "find"
+	--test-- "find bitset! char!"
+		;@@ https://github.com/Oldes/Rebol-issues/issues/2166
+		ABC: charset [#"A" #"B" #"C"]
+		--assert find ABC #"a"
+		--assert find ABC #"A"
+		--assert find/case ABC #"A"
+		--assert not find/case ABC #"a"
+		; finding integer value is always case-sensitive
+		--assert find ABC to-integer #"A"
+		--assert not find ABC to-integer #"a"
+		; pick is always case-sensitive
+		--assert pick ABC #"A"
+		--assert not pick ABC #"a"
+
+===end-group===
+
+
 ===start-group=== "complemented"
 
 	--test-- "comp-1"	--assert "make bitset! [not bits #{}]"   = mold charset [not]