src: namespace symbols clashing with lib

[vszakats]

lib/http.h and src/tool_sdecls.h both declared HTTPREQ_*
enums.

Rename src ones to have distinct names.

They are not included in the same code for now, but this may
change when bundling unit/libtests into single programs. But I
figure it'd be nice to make these unique regardless.

---

Question: Would it be better to merge them and move them to
curl_setup.h or someplace shared between lib and src?

curl/lib/http.h

Lines 36 to 43 in 6a9b710

	typedef enum {
	HTTPREQ_GET,
	HTTPREQ_POST,
	HTTPREQ_POST_FORM, /* we make a difference internally */
	HTTPREQ_POST_MIME, /* we make a difference internally */
	HTTPREQ_PUT,
	HTTPREQ_HEAD
	} Curl_HttpReq;

curl/src/tool_sdecls.h

Lines 116 to 123 in 6a9b710

	typedef enum {
	HTTPREQ_UNSPEC, /* first in list */
	HTTPREQ_GET,
	HTTPREQ_HEAD,
	HTTPREQ_MIMEPOST,
	HTTPREQ_SIMPLEPOST,
	HTTPREQ_PUT
	} HttpReq;