docs/libcurl: fix three minor man page format mistakes

[charles2910]

Hi there,

After the last upload of curl to Debian (8.4.0), samueloph noticed some lintian warnings about the manpages:

W: libcurl4-doc: groff-message troff:<standard input>:106: warning: macro '..' not defined [usr/share/man/man3/curl_global_trace.3.gz:1]
W: libcurl4-doc: groff-message troff:<standard input>:119: warning: macro 'BR' not defined [usr/share/man/man3/curl_getdate.3.gz:4]
W: libcurl4-doc: groff-message troff:<standard input>:25: warning: macro 'SH' not defined [usr/share/man/man3/curl_getdate.3.gz:1]
W: libcurl4-doc: groff-message troff:<standard input>:46: warning: macro 'TP' not defined [usr/share/man/man3/curl_getdate.3.gz:2]
W: libcurl4-doc: groff-message troff:<standard input>:47: warning: macro 'B' not defined [usr/share/man/man3/curl_getdate.3.gz:3]
W: libcurl4-doc: groff-message troff:<standard input>:64: warning: macro 'BN' not defined [usr/share/man/man3/CURLOPT_PROXY_TRANSFER_MODE.3.gz:1]
W: libcurl4-doc: groff-message troff:<standard input>:75: warning: expected numeric expression, got 'd' [usr/share/man/man3/libcurl.3.gz:1]

He asked me to take a look at it (I'm currently helping him a bit with packaging), so here we are. One problem was fixed already by e2006b5, but the others are still there and this commit fix them.

Note that lintian itself gave me a hint:

The check for manual pages uses the --warnings option to man to catch common problems, like a . or a ' at the beginning of a line as literal text. They are interpreted as Groff commands. Just reformat the paragraph so the characters are not at the beginning of a line. You can also add a zero-width space (&) in front of them.

This is my first contribution to curl, so I might have done things improperly. Please let me know if I should correct anything.

[jay]

Thanks