Remove all strcmp and strlen calls on Glyph.c[]

There were a few occurrences of strcmp and strlen being called on Glyph.c[],
which is not always null-terminated (this actually depends on the last values in
the buffer s in ttyread()). This patch replace all the calls to strcmp with a
test on c[0] directly or a call to tlinelen, and the one to strlen with utf8len.
I also took the opportunity to refactor getsel and tdumpline.

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
Render faint attribute

Faint text is implemented by allocating a new color at one-half
intensity of each of the r, g, b components, or if the text bold at the
same time, it is not made lighter.

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
Signed-off-by: Christoph Lohmann <20h@r-36.net>
Add 8 bit version of DECID

DECID version for 7 bits environments already was implemented in st.
This patch adds the 8 bit version of it.
Add 8 bit version of NEL

NEL version for 7 bits environments already was implemented in st.
This patch adds the 8 bit version of it.
Add 8 bit version of HTS

HTS version for 7 bits environments already was implemented in st.
This patch adds the 8 bit version of it.
Add 8 bit version of DCS, APC, PM, OSC

DCS, APC, PM, OSC version for 7 bits environments already was implemented
in st.  This patch adds the 8 bit version of it.