Port a lot more code to AARCH64

- Introduce epoll_pwait()
- Rewrite -ftrapv and ffs() libraries in C code
- Use more FreeBSD code in math function library
- Get significantly more tests passing on qemu-aarch64
- Fix many Musl long double functions that were broken on AARCH64

libc/tinymath/j1.c

@@ -144,6 +144,9 @@ s03 =  1.17718464042623683263e-06, /* 0x3EB3BFF8, 0x333F8498 */
 s04 =  5.04636257076217042715e-09, /* 0x3E35AC88, 0xC97DFF2C */
 s05 =  1.23542274426137913908e-11; /* 0x3DAB2ACF, 0xCFB97ED8 */
 
+/**
+ * Returns Bessel function of 𝑥 of first kind of order 1.
+ */
 double j1(double x)
 {
 	double z,r,s;
@@ -183,6 +186,9 @@ static const double V0[5] = {
   1.66559246207992079114e-11, /* 0x3DB25039, 0xDACA772A */
 };
 
+/**
+ * Returns Bessel function of 𝑥 of second kind of order 1.
+ */
 double y1(double x)
 {
 	double z,u,v;