Many changes for ELF shared libraries on Linux and Android

Handling more than 2 PT_LOAD (and thus more than 1 executable PT_LOAD)
required extensive changes.  But the bonus is the infrastructure
to support a different (de-)compression algorithm for each PT_LOAD.

https://github.com/upx/upx/issues/341   i386 .so decompression
https://github.com/upx/upx/issues/609   armv7 .so on Android
https://github.com/upx/upx/issues/625   amd64 .so execution
https://github.com/upx/upx/issues/654   armv7 .exe
Not yet: .so on MIPS, PowerPC, PowerPC64

src/p_elf_enum.h

@@ -249,9 +249,11 @@
         R_PPC64_JMP_SLOT = R_PPC_JMP_SLOT,
         R_X86_64_JUMP_SLOT = 7,
 
+        R_386_32 = 1,
         R_ARM_ABS32 = 2,
         R_ARM_GLOB_DAT = 21,
 
+        R_386_GLOB_DAT = 6,
         R_AARCH64_ABS64 = 257,
         R_AARCH64_GLOB_DAT = 1025,