allow some additional values for compiler testing

Allow compiler.370 to recognize a couple of additional values on the Make command line.
.

sys/unix/hints/include/compiler.370

@@ -55,6 +55,7 @@ CFLAGS+=-Wall -Wextra  \
 CFLAGS+=-pedantic
 CFLAGS+=-Wmissing-declarations
 #CFLAGS+=-Wformat=2
+CFLAGS+=-Wdiscarded-qualifiers
 
 # these are left out of the C++ flags
 CFLAGS+=-Wformat-nonliteral
@@ -234,6 +235,20 @@ ifeq "$(C23)" "1"
 HAVECSTD=c2x
 endif
 
+ifeq "$(c2x)" "1"
+HAVECSTD=c2x
+endif
+ifeq "$(C2X)" "1"
+HAVECSTD=c2x
+endif
+
+ifeq "$(c2y)" "1"
+HAVECSTD=c2y
+endif
+ifeq "$(C2Y)" "1"
+HAVECSTD=c2y
+endif
+
 ifneq "$(HAVECSTD)" ""
 CSTD = -std=$(HAVECSTD)
 endif