Fix bugs and make improvements

- Get clone() working on FreeBSD
- Increase some Python build quotas
- Add more atomic builtins to chibicc
- Fix ASAN poisoning of alloca() memory
- Make MODE= mandatory link path tinier
- Improve the examples folder a little bit
- Start working on some more resource limits
- Make the linenoise auto-complete UI as good as GNU readline
- Update compile.com, avoiding AVX codegen on non-AVX systems
- Make sure empty path to syscalls like opendir raises ENOENT
- Correctly polyfill ENOENT vs. ENOTDIR on the New Technology
- Port bestline's paredit features to //third_party/linenoise
- Remove workarounds for RHEL 5.0 bugs that were fixed in 5.1

libc/calls/ucontext.h

@@ -5,56 +5,6 @@
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
-#define REG_R8      REG_R8
-#define REG_R9      REG_R9
-#define REG_R10     REG_R10
-#define REG_R11     REG_R11
-#define REG_R12     REG_R12
-#define REG_R13     REG_R13
-#define REG_R14     REG_R14
-#define REG_R15     REG_R15
-#define REG_RDI     REG_RDI
-#define REG_RSI     REG_RSI
-#define REG_RBP     REG_RBP
-#define REG_RBX     REG_RBX
-#define REG_RDX     REG_RDX
-#define REG_RAX     REG_RAX
-#define REG_RCX     REG_RCX
-#define REG_RSP     REG_RSP
-#define REG_RIP     REG_RIP
-#define REG_EFL     REG_EFL
-#define REG_CSGSFS  REG_CSGSFS
-#define REG_ERR     REG_ERR
-#define REG_TRAPNO  REG_TRAPNO
-#define REG_OLDMASK REG_OLDMASK
-#define REG_CR2     REG_CR2
-
-enum GeneralRegister {
-  REG_R8,
-  REG_R9,
-  REG_R10,
-  REG_R11,
-  REG_R12,
-  REG_R13,
-  REG_R14,
-  REG_R15,
-  REG_RDI,
-  REG_RSI,
-  REG_RBP,
-  REG_RBX,
-  REG_RDX,
-  REG_RAX,
-  REG_RCX,
-  REG_RSP,
-  REG_RIP,
-  REG_EFL,
-  REG_CSGSFS,
-  REG_ERR,
-  REG_TRAPNO,
-  REG_OLDMASK,
-  REG_CR2
-};
-
 struct XmmRegister {
   uint64_t u64[2];
 };