Add MPFR detection

example/Makefile

@@ -23,6 +23,7 @@
 CC=cc -std=c99
 CFLAGS=-Wall -W -pedantic -Wshadow -Wpointer-arith -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes -Wswitch-default -Wswitch-enum -Wcast-align -Wpointer-arith -Wbad-function-cast -Wstrict-overflow=5 -Wstrict-prototypes -Winline -Wundef -Wnested-externs -Wcast-qual -Wshadow -Wunreachable-code -Wlogical-op -Wstrict-aliasing=2 -Wredundant-decls -Wold-style-definition -Wno-unused-function -g
 GMP_DIR=
+MPFR_DIR=$(GMP_DIR)
 CPPFLAGS=-I..
 LDFLAGS=-pthread
 RM=rm -f
@@ -39,6 +40,8 @@ all: config
 config:
 	printf "#include <gmp.h>\nint main(void){mpz_t z; mpz_init(z); return 0;}\n" > config-test.c
 	$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS)  -I$(GMP_DIR)/include -L$(GMP_DIR)/lib -lgmp config-test.c -o config-test.exe 2> /dev/null && echo "-DHAVE_GMP=1  -I$(GMP_DIR)/include -L$(GMP_DIR)/lib -lgmp" > config || echo "-DHAVE_GMP=0" > config
+	printf "#include <mpfr.h>\nint main(void){mpfr_t z; mpfr_init(z); return 0;}\n" > config-test.c
+	$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS)  -I$(GMP_DIR)/include -I$(MPFR_DIR)/include -L$(GMP_DIR)/lib -L$(MPFR_DIR)/lib -lmpfr -lgmp config-test.c -o config-test.exe 2> /dev/null && (echo "-DHAVE_GMP=1 -DHAVE_MPFR=1  -I$(GMP_DIR)/include -L$(GMP_DIR)/lib -I$(MPFR_DIR)/include -L$(MPFR_DIR)/lib -lmpfr -lgmp" > config )
 	$(RM) config-test.c config-test.exe
 
 clean: