Fix $smart_wrap to not be disabled by whitespace-prefixed lines. (closes #3857)

Fix $smart_wrap to not be disabled by whitespace-prefixed lines. (closes #3857)

changeset:737102af74eb fixed a folded header display issue with $smart_wrap
by disabling $smart_wrap for lines beginning with whitespace.

Unfortunately, this turns off smart wrapping in the body of an email
too, even when the line has other whitespace breaks in it.

An earlier commit, changeset:125076e0fdfa added an infinite loop fix
when MUTT_PAGER_NSKIP is set, by disabling the smart_wrap if the space
backtracking went to the beginning of the line.  That is, a line
beginning with 1+ whitespace followed by a single long word.

Extend this second commit by always disabling the smart_wrap in that
case, not just when MUTT_PAGER_NSKIP is set.  This also solves the
folded header issue without other side effects.