Correct the compiler warnings

[MathieuDutSik]

With g++ 7.2.0 we have compiler warnings such as
/home/mathieu/GITall/GIT/Satisfiability/minisat/minisat/utils/Options.h:285:29: warning: invalid suffix on literal; C++11 requires a space between literal and string macro [-Wliteral-suffix] fprintf(stderr, "%4"PRIi64, range.begin);

Could this be addressed?

[dmdmdm]

I band-aided that by changing file mtl/template.mk line 23 from:

CFLAGS    ?= -Wall -Wno-parentheses

to:

CFLAGS    ?= -Wno-parentheses -fpermissive -Wno-literal-suffix

Of course, this is a hack so I'm not doing a pull request.