REORG: polling: rename "spec_e" to "state" and "spec_p" to "cache"

We're completely changing the way FDs will be polled. There will be no
more speculative I/O since we'll know the exact FD state, so these will
only be cached events.

First, let's fix a few field names which become confusing. "spec_e" was
used to store a speculative I/O event state. Now we'll store the whole
R/W states for the FD there. "spec_p" was used to store a speculative
I/O cache position. Now let's clearly call it "cache".
diff --git a/include/proto/fd.h b/include/proto/fd.h
index a67a320..3563a08 100644
--- a/include/proto/fd.h
+++ b/include/proto/fd.h
@@ -97,11 +97,11 @@
 /* allocate an entry for a speculative event. This can be done at any time. */
 static inline void alloc_spec_entry(const int fd)
 {
-	if (fdtab[fd].spec_p)
+	if (fdtab[fd].cache)
 		/* FD already in speculative I/O list */
 		return;
 	fd_nbspec++;
-	fdtab[fd].spec_p = fd_nbspec;
+	fdtab[fd].cache = fd_nbspec;
 	fd_spec[fd_nbspec-1] = fd;
 }
 
@@ -113,16 +113,16 @@
 {
 	unsigned int pos;
 
-	pos = fdtab[fd].spec_p;
+	pos = fdtab[fd].cache;
 	if (!pos)
 		return;
-	fdtab[fd].spec_p = 0;
+	fdtab[fd].cache = 0;
 	fd_nbspec--;
 	if (likely(pos <= fd_nbspec)) {
 		/* was not the last entry */
 		fd = fd_spec[fd_nbspec];
 		fd_spec[pos - 1] = fd;
-		fdtab[fd].spec_p = pos;
+		fdtab[fd].cache = pos;
 	}
 }