if calloc() doesn't allocate memory for struct tvm_ctx,
there may be NULL pointer dereferencing, i.e. vm->mem, vm->prog.
So the vm pointer verification must be before it is used.
Also, there is the same situation with vm->mem and stack creation.
During preprocessing, we find directives, and if they specify including
other source files, we remove the directive, allocate a new block of
memory, copy the first block, append the new source file, and append the
second block.
Previously, the value of the source pointer was passed into the
preprocessing function. When the memory would be (re)allocated, the
pointer value could change, but the original pointer would not be
updated.
Now, the pointer is passed by address, and updated when the memory it
points to changes.
This commit refactors the project using a single, consistent coding
style, derived from the Linux Kernel Coding Style, available here:
https://www.kernel.org/doc/Documentation/CodingStyle
This includes, but is not limited to:
* Removal of typedefs, especially for structs
* Limiting lines to a reasonable length, 80 characters, mostly
* K&R style braces
* Removal of CamelCase
