USDT helpers do not support multiple processes attaching to the same probe

When I execute ```dbslower postgres``` I get the following:

```
/virtual/main.c:13:19: error: redefinition of '_bpf_readarg_probe_start_1'
static inline int _bpf_readarg_probe_start_1(struct pt_regs *ctx, void *dest, size_t len) {
^
/virtual/main.c:2:19: note: previous definition is here
static inline int _bpf_readarg_probe_start_1(struct pt_regs *ctx, void *dest, size_t len) {
^
/virtual/main.c:18:19: error: redefinition of '_bpf_readarg_probe_end_1'
static inline int _bpf_readarg_probe_end_1(struct pt_regs *ctx, void *dest, size_t len) {
^
/virtual/main.c:7:19: note: previous definition is here
static inline int _bpf_readarg_probe_end_1(struct pt_regs *ctx, void *dest, size_t len) {
^
2 errors generated.
```

There are multiple ```postgres``` instances running.

There are other errors as well, but those are solved by changing ```#include ``` to ```#include ```

Using latest master ( d5e5bb3 ) with clang version 3.8.1 on Fedora 24.