Fix the inline replace of kprobe args

Fix the inline replace of kprobe args

The way in which args 1+ were being replaced in the C file was
fragile. Instead, assign the registers from ptregs into the function
arguments as the first statement(s) in the body of the function.
e.g.:
int sys_clone(struct ptregs *ctx, struct request *req) {
  // do something with req
}
becomes:
int sys_clone(struct ptregs *ctx, struct request *req) {
  req = ctx->di;
  // do something with req

Fixes: #192
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>