Fix segfault in matrix::connection, fix typo in netreturn generation, update matrix-send utility

makefile

@@ -23,10 +23,11 @@ OBJDIR::=obj
 DEPDIR::=$(OBJDIR)/dep
 LIBDIR::=lib
 INCLUDE_DIRS::=include
-CXXFLAGS::=-g -std=c++17 -Wall -pedantic -Wextra
+CXXFLAGS::=-std=c++17 -Wall -pedantic -Wextra
 EXT::=cpp
 MAIN_LIBRARY::=rmatrix
-SHARED?=1
+SHARED?=0
+RELEASE?=0
 
 ifneq ($(WINDOWS),1)
 	CXX::=g++
@@ -58,9 +59,11 @@ else
 	INTERNAL_MAIN_LIBRARY::=lib$(MAIN_LIBRARY).a
 endif
 
-
-all: CXXFLAGS+=-O0
-release: CXXFLAGS+=-O2
+ifeq ($(RELEASE),1)
+	CXXFLAGS+=-O2
+else
+	CXXFLAGS+=-O0 -g
+endif
 
 memchk: LDFLAGS+=-fsanitize=address -fno-omit-frame-pointer -fno-optimize-sibling-calls
 memchk: CXXFLAGS+=-O0 -fsanitize=address -fno-omit-frame-pointer -fno-optimize-sibling-calls
@@ -107,9 +110,7 @@ $(INTERNAL_MAIN_LIBRARY): $(OBJECTS)
 endif #shared
 
 .PHONY: memchk
-.PHONY: release
 memchk: all
-release: all
 
 .PHONY: utils
 utils: matrix-send