tests/hgterm.ti

revlog: have an explicit "pack_header" method

Having to pass the version header when retrieving the binary version of every
single entry is a bit silly. So we extract that special logic in its own method.
This also prepare the move to newer revlog format, not storing the header within
an actual entry…

Differential Revision: https://phab.mercurial-scm.org/D10510

hgterm,
	am, km, mir, msgr, xenl,
	colors#8, cols#80, it#8, lines#24, pairs#64,
	acsc=``aaffggiijjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~,
	bel=^G, bold=\E[1m, clear=\E[H\E[2J, cr=\r,
	csr=\E[%i%p1%d;%p2%dr, cub=\E[%p1%dD, cub1=\b,
	cud=\E[%p1%dB, cud1=\n, cuf=\E[%p1%dC, cuf1=\E[C,
	cup=\E[%i%p1%d;%p2%dH, cuu=\E[%p1%dA, cuu1=\E[A,
	dch=\E[%p1%dP, dch1=\E[P, dl=\E[%p1%dM, dl1=\E[M,
	ed=\E[J, el=\E[K, enacs=\E)0, home=\E[H, ht=\t,
	hts=\EH, il=\E[%p1%dL, il1=\E[L, ind=\n,
	is2=\E[m\E[?7h\E[4l\E>\E7\E[r\E[?1;3;4;6l\E8, kbs=\b,
	kcub1=\EOD, kcud1=\EOB, kcuf1=\EOC, kcuu1=\EOA,
	kdch1=\E[3~, kf1=\E[11~, kf10=\E[21~, kf11=\E[23~,
	kf12=\E[24~, kf13=\E[25~, kf14=\E[26~, kf15=\E[28~,
	kf16=\E[29~, kf17=\E[31~, kf18=\E[32~, kf19=\E[33~,
	kf2=\E[12~, kf20=\E[34~, kf3=\E[13~, kf4=\E[14~,
	kf5=\E[15~, kf6=\E[17~, kf7=\E[18~, kf8=\E[19~,
	kf9=\E[20~, kfnd=\E[1~, kich1=\E[2~, kmous=\E[M,
	knp=\E[6~, kpp=\E[5~, kslt=\E[4~, op=\E[m, rc=\E8,
	rev=\E[7m, ri=\EM, rmacs=^O, rmcup=\E[2J\E[?47l\E8,
	rmir=\E[4l, rmkx=\E[?1l\E>, rmso=\E[m, rmul=\E[m,
	rs2=\E[m\E[?7h\E[4l\E>\E7\E[r\E[?1;3;4;6l\E8, sc=\E7,
	setab=\E[4%p1%dm, setaf=\E[3%p1%dm, sgr0=\E[m,
	smacs=^N, smcup=\E7\E[?47h, smir=\E[4h,
	smkx=\E[?1h\E=, smso=\E[7m, smul=\E[4m, tbc=\E[3g,
	u6=\E[%i%d;%dR, u7=\E[6n, u8=\E[?1;2c, u9=\E[c,