Add C++ Guards#42

Fully tested. Output: ``` libtool --mode=compile --tag=CC cc -I. -Wall -std=c99 -O2 -o t/static_xterm.lo -c t/static_xterm.c libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/static_xterm.c -fPIC -DPIC -o t/.libs/static_xterm.o libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/static_xterm.c -o t/static_xterm.o >/dev/null 2>&1 libtool --mode=link --tag=CC cc -o t/static_xterm.t libunibilium.la t/static_xterm.lo ^Cmake: *** [Makefile:81: t/static_xterm.t] Interrupt make: *** Deleting intermediate file 't/static_xterm.lo' gitpod /workspace/unibilium $ make test -j8 libtool --mode=compile --tag=CC cc -I. -Wall -std=c99 -O2 -o t/static_xterm.lo -c t/static_xterm.c libtool --mode=compile --tag=CC cc -I. -Wall -std=c99 -O2 -o t/static_tmux.lo -c t/static_tmux.c libtool --mode=compile --tag=CC cc -I. -Wall -std=c99 -O2 -o t/wide-format.lo -c t/wide-format.c libtool --mode=compile --tag=CC cc -I. -Wall -std=c99 -O2 -o t/if-then-else.lo -c t/if-then-else.c libtool --mode=compile --tag=CC cc -I. -Wall -std=c99 -O2 -o t/static_screen.lo -c t/static_screen.c libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/static_xterm.c -fPIC -DPIC -o t/.libs/static_xterm.o libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/static_screen.c -fPIC -DPIC -o t/.libs/static_screen.o libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/wide-format.c -fPIC -DPIC -o t/.libs/wide-format.o libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/if-then-else.c -fPIC -DPIC -o t/.libs/if-then-else.o libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/static_tmux.c -fPIC -DPIC -o t/.libs/static_tmux.o libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/wide-format.c -o t/wide-format.o >/dev/null 2>&1 libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/if-then-else.c -o t/if-then-else.o >/dev/null 2>&1 libtool --mode=link --tag=CC cc -o t/wide-format.t libunibilium.la t/wide-format.lo libtool --mode=link --tag=CC cc -o t/if-then-else.t libunibilium.la t/if-then-else.lo libtool: link: cc -o t/.libs/wide-format.t t/.libs/wide-format.o ./.libs/libunibilium.so libtool: link: cc -o t/.libs/if-then-else.t t/.libs/if-then-else.o ./.libs/libunibilium.so libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/static_screen.c -o t/static_screen.o >/dev/null 2>&1 libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/static_xterm.c -o t/static_xterm.o >/dev/null 2>&1 libtool: compile: cc -I. -Wall -std=c99 -O2 -c t/static_tmux.c -o t/static_tmux.o >/dev/null 2>&1 libtool --mode=link --tag=CC cc -o t/static_screen.t libunibilium.la t/static_screen.lo libtool: link: cc -o t/.libs/static_screen.t t/.libs/static_screen.o ./.libs/libunibilium.so libtool --mode=link --tag=CC cc -o t/static_xterm.t libunibilium.la t/static_xterm.lo libtool: link: cc -o t/.libs/static_xterm.t t/.libs/static_xterm.o ./.libs/libunibilium.so libtool --mode=link --tag=CC cc -o t/static_tmux.t libunibilium.la t/static_tmux.lo libtool: link: cc -o t/.libs/static_tmux.t t/.libs/static_tmux.o ./.libs/libunibilium.so prove -j8 t/00_load.t ................. ok t/if-then-else.t ............ ok t/wide-format.t ............. ok t/static_screen-256color.t .. ok t/static_screen.t ........... ok t/static_tmux.t ............. ok t/static_xterm-256color.t ... ok t/static_xterm.t ............ ok All tests successful. Files=8, Tests=3137, 0 wallclock secs ( 0.25 usr 0.02 sys + 0.24 cusr 0.36 csys = 0.87 CPU) Result: PASS rm t/wide-format.lo t/static_xterm.lo t/static_screen.lo t/if-then-else.lo t/static_tmux.lo ```