[libc] Enable string to integer conversion functions in the default build

[michaelrj]

Summary

Adds atoi, atol, atoll, strtol, strtoll, strtoul, and strtoull to the
list of entrypoints for Windows and aarch64 linux, as well as moving
them out of the LLVM_LIBC_FULL_BUILD condition for x86_64 linux.

[sivachandra]

We should make all configs uniform. So, can we move these functions to the default config for x86_64 and aarch64 also?

[michaelrj]

added the functions to aarch64, moved them out of the full build condition on x86_64, and updated the commit message.

[michaelrj]

fix issues that came up in testing

The issues are as follows:

1. Failure to build with FULL_BUILD off, due to the stdlib source not being included
2. The string conversion tests not being run with FULL_BUILD off
3. The atoi, atol, and atoll tests not being run at all (no CMake rule)
4. A few typos found in the atol and atoll tests.

[sivachandra]

Accepting but ideally we should separate concerns - the typos and missing CMake targets part should have been done in a separate patch.

[michaelrj]

I will split patches like this in the future. For this patch I have run the tests on an aarch64 host, and they passed, so I will run one last check and then submit it.

libc/config/windows/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.string.strncpy
     libc.src.string.strnlen
     libc.src.string.strpbrk
     libc.src.string.strrchr
     libc.src.string.strspn
     libc.src.string.strstr
     libc.src.string.strtok
     libc.src.string.strtok_r
+
+    # stdlib.h entrypoints
+    libc.src.stdlib.atoi
+    libc.src.stdlib.atol
+    libc.src.stdlib.atoll
+    libc.src.stdlib.strtol
+    libc.src.stdlib.strtoll
+    libc.src.stdlib.strtoul
+    libc.src.stdlib.strtoull
 )
 
 set(TARGET_LIBM_ENTRYPOINTS
     # fenv.h entrypoints
     libc.src.fenv.feclearexcept
     libc.src.fenv.fegetenv
     libc.src.fenv.fegetexceptflag
     libc.src.fenv.fegetround