Fix portability problem in techo()

ISCONTROL chechks if a value is between 0 and 0x1f or
between 0x80 and 0x9f. Char signess depends of architecture
and compiler, so in some environment the second case is
always false (and wrong), Techo() calls ISCONTROL with a
char variable, whose type cannot be changed because tpuc()
expects a pointer to char, so the solution is to insert a
cast in the call to ISCONTROL.
Convert VT102ID to a config variable

VT102ID is the sequence that the terminal returns when it is inquired
to identify itself. This value should be configurable in the same
way that another st parameters.
added .gitignore file
symlinked config.def.h to config.h
initial commit of my config.def.h
default font is now DejaVu Sans Mono for Powerline