Enforce strict mode of jsmn.

If no strict mode of jsmn is enforced, then the correct amount of
json elements would have to be checked to avoid segmentation faults
on malformed state files:

$ echo '{ "focusedMonitorId" }' > malformed-state
$ bspwm -s malformed-state
Segmentation fault
$ _

Signed-off-by: Tobias Stoeckmann <[email protected]>

Makefile

@@ -2,7 +2,7 @@ VERCMD  ?= git describe 2> /dev/null
 VERSION := $(shell $(VERCMD) || cat VERSION)
 
 CPPFLAGS += -D_POSIX_C_SOURCE=200809L -DVERSION=\"$(VERSION)\"
-CFLAGS   += -std=c99 -pedantic -Wall -Wextra
+CFLAGS   += -std=c99 -pedantic -Wall -Wextra -DJSMN_STRICT
 LDFLAGS  ?=
 LDLIBS    = $(LDFLAGS) -lm -lxcb -lxcb-util -lxcb-keysyms -lxcb-icccm -lxcb-ewmh -lxcb-randr -lxcb-xinerama -lxcb-shape