man-pages.7: Add preferred terms "uppercase" and "lowercase"

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man7/man-pages.7

@@ -613,6 +613,7 @@ filename	file name
 filesystem	file system
 hostname	host name
 inode	i-node
+lowercase	lower case, lower-case
 pathname	path name
 pseudoterminal	pseudo-terminal
 privileged port	T{
@@ -644,6 +645,7 @@ super-block
 T}
 timestamp	time stamp
 timezone	time zone
+uppercase	upper case, upper-case
 usable	useable
 user space	userspace
 username	user name