Minor fixes: gxpkg, std/text/char-set, README (#1023) #2764

Job	Run time
build	41m 58s
build (--disable-shared)	57m 1s
build (--with-gambit=master)	19m 55s
build (--with-gambit=master, --disable-shared)	25m 41s
	2h 24m 35s

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