maint: convert `...' to '...' in --help output

All affected lines end with \ or \n\, so run this command
until it produces no new changes (4 times):
  git grep -E -l '`[^ ]+'\''.*\\' src \
    |xargs perl -pi -e 's/`([^ ]+'\''.*\\)/'\''$1/'

1 files changed, 4 insertions, 4 deletions

diff --git a/src/split.c b/src/split.c
index d0abd65fb..8a5736363 100644
--- a/src/split.c
+++ b/src/split.c
@@ -184,7 +184,7 @@ Usage: %s [OPTION]... [INPUT [PREFIX]]\n\
               program_name);
       fputs (_("\
 Output fixed-size pieces of INPUT to PREFIXaa, PREFIXab, ...; default\n\
-size is 1000 lines, and default PREFIX is `x'.  With no INPUT, or when INPUT\n\
+size is 1000 lines, and default PREFIX is 'x'.  With no INPUT, or when INPUT\n\
 is -, read standard input.\n\
 \n\
 "), stdout);
@@ -196,11 +196,11 @@ Mandatory arguments to long options are mandatory for short options too.\n\
   -b, --bytes=SIZE        put SIZE bytes per output file\n\
   -C, --line-bytes=SIZE   put at most SIZE bytes of lines per output file\n\
   -d, --numeric-suffixes  use numeric suffixes instead of alphabetic\n\
-  -e, --elide-empty-files  do not generate empty output files with `-n'\n\
+  -e, --elide-empty-files  do not generate empty output files with '-n'\n\
       --filter=COMMAND    write to shell COMMAND; file name is $FILE\n\
   -l, --lines=NUMBER      put NUMBER lines per output file\n\
   -n, --number=CHUNKS     generate CHUNKS output files.  See below\n\
-  -u, --unbuffered        immediately copy input to output with `-n r/...'\n\
+  -u, --unbuffered        immediately copy input to output with '-n r/...'\n\
 "), DEFAULT_SUFFIX_LENGTH);
       fputs (_("\
       --verbose           print a diagnostic just before each\n\
@@ -215,7 +215,7 @@ N       split into N files based on size of input\n\
 K/N     output Kth of N to stdout\n\
 l/N     split into N files without splitting lines\n\
 l/K/N   output Kth of N to stdout without splitting lines\n\
-r/N     like `l' but use round robin distribution\n\
+r/N     like 'l' but use round robin distribution\n\
 r/K/N   likewise but only output Kth of N to stdout\n\
 "), stdout);
       emit_ancillary_info ();