doc: apply man page formatting suggestions from manpage-l10n

* src/basenc.c: Add (1) to base64 and base32 references.
* src/cksum.c. Likewise for cksum references.
* src/echo.c: Use "bell" in descriptions rather than BEL.
* src/printf.c: Likewise.
* src/id.c: Separate -u,-U,-G so marked up appropriately.
Fixes https://bugs.gnu.org/80904

src/basenc.c

@@ -119,7 +119,7 @@ Base%d encode or decode FILE, or standard input, to standard output.\n\
 #if BASE_TYPE == 42
       oputs (_("\
       --base64\n\
-         same as 'base64' program (RFC4648 section 4)\n\
+         same as base64(1) program (RFC4648 section 4)\n\
 "));
       oputs (_("\
       --base64url\n\
@@ -131,7 +131,7 @@ Base%d encode or decode FILE, or standard input, to standard output.\n\
 "));
       oputs (_("\
       --base32\n\
-         same as 'base32' program (RFC4648 section 6)\n\
+         same as base32(1) program (RFC4648 section 6)\n\
 "));
       oputs (_("\
       --base32hex\n\

src/cksum.c

@@ -502,7 +502,7 @@ Usage: %s [OPTION]... [FILE]...\n\
 Print or check %s checksums.\n\
 "), DIGEST_TYPE_STRING);
         fputs (_("\
-Legacy interface to the cksum utility.\n\
+Legacy interface to the cksum(1) utility.\n\
 "), stdout);
       }
     else
@@ -517,7 +517,7 @@ Print or check %s (%d-bit) checksums.\n\
               DIGEST_TYPE_STRING,
               DIGEST_BITS);
       fputs (_("\
-Legacy interface to the cksum utility.\n\
+Legacy interface to the cksum(1) utility.\n\
 "), stdout);
 #endif
 

src/echo.c

@@ -74,7 +74,7 @@ If -e is in effect, the following sequences are recognized:\n\
 "), stdout);
   fputs (_("\
   \\\\      backslash\n\
-  \\a      alert (BEL)\n\
+  \\a      alert (bell)\n\
   \\b      backspace\n\
   \\c      produce no further output\n\
   \\e      escape\n\

src/id.c

@@ -115,11 +115,11 @@ or (when USER omitted) for the current process.\n\
 "));
       oputs (_("\
   -n, --name\n\
-         print a name instead of a number, for -u,-g,-G\n\
+         print a name instead of a number, for -u, -g, -G\n\
 "));
       oputs (_("\
   -r, --real\n\
-         print the real ID instead of the effective ID, with -u,-g,-G\n\
+         print the real ID instead of the effective ID, with -u, -g, -G\n\
 "));
       oputs (_("\
   -u, --user\n\

src/printf.c

@@ -69,7 +69,7 @@ FORMAT controls the output as in C printf.  Interpreted sequences are:\n\
 "), stdout);
       fputs (_("\
   \\\\      backslash\n\
-  \\a      alert (BEL)\n\
+  \\a      alert (bell)\n\
   \\b      backspace\n\
   \\c      produce no further output\n\
   \\e      escape\n\