As far as the set of .cpp files which are using vecmat.h are
concerned, `Zero_vector` is out of reach for the compiler optimizer,
because it is extern / lives in a separate translation unit. An
expression like `x == Zero_vector` or `v = Zero_vector` thus has to
perform memory loads (for Zero_vector's x,y,z parts) before
comparison or copying, respectively. By using an immediate zero
vector `vector{}` instead, the unnecessary extra loads should go
away.
I present exhibit A:
```
void copyxx(vector *x) { *x = Zero_vector; }
4905e0: 48 8b 05 41 c0 56 00 movq 0x56c041(%rip),%rax # 9fc628 <Zero_vector>
4905e7: 48 89 07 movq %rax,(%rdi)
4905ea: 8b 05 40 c0 56 00 movl 0x56c040(%rip),%eax # 9fc630 <Zero_vector+0x8>
4905f0: 89 47 08 movl %eax,0x8(%rdi)
4905f3: c3 ret
```
vs.
```
void copyxx(vector *x) { *x = vector{}; }
4905c0: 48 c7 07 00 00 00 00 movq $0x0,(%rdi)
4905c7: c7 47 08 00 00 00 00 movl $0x0,0x8(%rdi)
4905ce: c3 ret
```
In `psrand.h` it attempts to undefine RAND_MAX and then redefine it.
This may work on some compilers but G++/Clang. To resolve this error
RAND_MAX was renamed to D3_RAND_MAX but **only** in files that
included `psrand.h`. The code behavior should restored to that of the
official release.
Join the license header with historical comments using a separator so IDEs can correctly parse the initial header.
Also use .gitattributes to ensure all files are LF.
The MACINTOSH define refers to MacOS Classic (not OS X) which we do not
plan to support. Rather than carry the cruft forever, let's delete it.
NOTE: legacy/ is unused but we're keeping it around, so MACINTOSH uses
there are left alone.
Process used for this commit:
```
git rm -r mac
find . \( -iname "*.c" -or -iname "*.cpp" -or -iname "*.h" \) \
-exec unifdef -UMACINTOSH -o {} {} \;
git restore legacy
git add .
```
Test Plan:
On Mac, build both Debug and Release
```
cmake --build --preset mac --config Debug
cmake --build --preset mac --config Release
```
